Is it acceptable to start a sentence with the preposition 'except' rather than 'except for'?

The sentence

Except the buildings built towards the end of his life, the buildings erected in Istanbul can be assumed to be his.

was recently used in a question here.

I edited to replace 'except' with the compound preposition 'except for'. I'm very unhappy with the original, but don't like to assume my gut reactions are necessarily correct.

CDO gives:

Except or except for? from English Grammar Today

We often use except and except for as prepositions to mean ‘not including’ or ‘excluding’. They are followed by a noun or noun phrase or a wh-clause. Both except and except for are correct after a noun:

I like all fruit except (for) oranges. (excluding oranges)

Except for Louisa, who’s away in Berlin this weekend, we’ll all be at the party.

She likes going to most sports events, except cricket matches.

This shows the choice of 'Except for' to start a sentence-initial prepositional phrase, but does not go so far as to state that the choice of the simple preposition is incorrect.

The nearest (but really reversed) question I can find on ELU is essentially

Is "Are there any vegetables except for asparagus?" correct?

to which Peter Shor provides the tantalysing answer (with which I largely agree):

I think what's wrong is the "for". [I'd say 'very iffy' in all but some unusual contexts]

Are there any vegetables except asparagus?

The grammar of when to use "except for" and when to use "except" is governed by [a] quite complex set of rules (often, you can use either). There probably is a correct and complete description of how this works somewhere on the internet, but I haven't found it, so I can't tell you why you should use "except" here; but it just feels right.

Can authorities be found giving this correct and complete description of the complex set of rules governing when to use "except for" and when to use "except" , on the internet or elsewhere?

I'm not an authority but anyway here is my answer. Firstly I want to point out that the occurrence of the collocation "except for" actually splits into two cases.

In one case it is a single lexical unit that is a preposition, hence accepting only noun phrases or equivalents as its 'object':

Everyone knew he was a fool except for himself.

The greedy want everything except for what they need.

In the other case the "for" actually belongs to a prepositional phrase, and it follows the usage of "except" such as in:

It offers a similar buffer option, except for books instead of video.

Here it parses as "similar except { for { { books } instead of { video } } }". Here "except for books instead of video" adverbially modifies "similar". Likewise:

He was blameless except in this matter. (takes an adverbial phrase and modifies "blameless")

He never takes advice except from Mother. (takes an adverbial phrase and modifies "takes advice")

The museum is always open except on Mondays. (takes an adverbial phrase and modifies "always open")

She ate everything except the meat. (takes a noun phrase and modifies "everything")

They will do nothing except sit here. (takes a verb phrase and modifies "do nothing")

I did not come except to help. (takes an infinitive and modifies "come")

The type of phrase Y that can be modified by an "except X" phrase has to be of the same type as X, except when X is an adverbial phrase and Y can be modified by X directly. Here are more actual examples with the "except" clause fronted:

Except among ideologues, there’s no ideal solution to these problems, and every remedy carries trade-offs. (Washington Post (2014))

Except among homesick Israeli immigrants and some Orthodox Jews who see living in the land of Israel as a religious imperative, there are precious few American Jews who ... (NY Times (2014))

Except among students of the modern papacy, Pius XI (Achille Ratti) remains an obscure figure. (Washington Post (2013))

Except under unusual circumstances, you should use the grammar and vocabulary of standard written English for these purposes. (NY Times (2012))

Except under khamsin conditions, nights in the desert are rarely very hot and may feel pleasantly fresh after the dry heat of the day. (BBC (2012))

Except when patients have been given blood or proteins intravenously, a rapid increase in total plasma protein concentration is always due to a decrease in the volume of distribution, basically to dehydration. (Journal for Respiratory Care & Sleep Medicine (2009))

Except possibly where a locally important species is very sensitive, freshwater aquatic life and their uses should not be affected unacceptably ... (US EPA (2004))

Except possibly under unusual circumstances not present here, we would not find a single conviction for a misdemeanor offense to be ... (US Justice (1988))

Except as provided below, no part of a White Paper may be reproduced in any material form ... (BBC)

Except with the prior approval of the court, the Secret Service shall not ... (US Code)

Except in the case of fraud, any action to recover penalties under this chapter shall be barred. (some US statute (2012))

Except on Israel, Unity Is Elusive At Islamic Summit (NY Times (1981))

Except these, there is no experimental indication for CP violation. (Physics Letters B (2004))

Except this there is nothing worthy of inspection. (The Description of Greece (1824))

There is also a specific usage with the subjunctive that seems less frequent now:

I will not go except you come with me. (normally it is "except if you ..." or "unless you ...")

Except one be born anew, he cannot see the kingdom of God. (ASV, Darby's, KJV)

Except a creature be part coward it is not a compliment to say it is brave. (Mark Twain)

I may have missed some details but I believe this kind of explanation is an adequate one for the major similarities and differences between "except" and "except for". For example it explains why we can say the first but not the second in each of the following examples:

I have not seen it except for when I was a child ("when I was a child" is a noun phrase)

*I have not seen it except for as a child ("as a child" is not a noun phrase)

You can take anything except this. ("this" is a noun phrase like "anything")

*You can take except this. ("this" is a noun phrase but there is none before "except")

So finally my answer to the original question is that both are valid English and mean exactly the same thing, although it might be better to delete redundancy:

Except [for] those built towards the end of his life, the buildings erected in Istanbul can be assumed to be his.

I grant that examples of sentence-initial "except" with noun phrases are rare, but since "except" with non-noun phrases aren't avoided at the beginning of proper sentences, I think the rarity for noun phrases is perhaps due to the fact that sentence-initial "except" is frequently used to join whole sentences. If that is so, then it may be that "except for" is used for noun phrases simply because it makes it easier to process. I myself would probably have chosen to use "except for", but I did not find the other one odd.

A review of the Oxford English Dictionary (OED) entry for the word except is availing. OED editors identify three senses of the word: in one it is an adjective, in the second a preposition, and in the third a conjunction (so except is not in all cases a preposition).

The adjective sense (with meaning similar to "excepted") is no longer in use in Modern English, but is probably the earliest as it hews closest to the Latin word. Two examples from 16th century texts:

1526 The greatest synner that is maye attayne therto, & none be except.
1535 Kynge Asa caused it be proclamed in all Iuda: Here be no man excepte.

The preposition sense is glossed as "Excepting, with the exception of, save, but." Since well-behaved prepositions in English are followed by a noun phrase, the preposition sense necessarily lacks "for". Examples from OED show the prepositional phrase formed from except coming at the end of the sentence.

1616 France is reuolted from the English quite, Except some petty Townes.
1766 The rabble of mankind..know nothing of liberty except the name.

The U.S. Constitution (Art. 1, Sec. 10) includes an example of prepositional except:

No State shall, without the Consent of the Congress, lay any Imposts or Duties on Imports or Exports, except what may be absolutely necessary for executing its inspection Laws...

Finally is the sense where except functions (according to OED) as a subordinating conjunction. This is the most widespread use today. OED says except must be followed by an "adverbial phrase" or a clause. The adverbial phrase can be a true adverb, a prepositional phrase, or a non-finite verb phrase. The clause is typically in subjunctive mood. Use of conjunction except with a clause as it is very common in Early Modern English (but sounds archaic today). Here are some examples from the book of Matthew in the King James Bible. The subordinate clause starting with except appears both before and after the main clause (subordinate clauses bolded in examples, main clauses in square brackets). Incidentally, there are no examples of except for + [Noun Phrase] in the King James New Testament.

5:20 For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, [ye shall in no case enter into the kingdom of heaven].
12:29 Or else [how can one enter into a strong man's house, and spoil his goods], except he first bind the strong man?
18:3 Verily I say unto you, Except ye be converted, and become as little children, [ye shall not enter into the kingdom of heaven].
19:9 And I say unto you, [Whosoever shall put away his wife], except it be for fornication, and shall marry another, committeth adultery.

Except for followed by a noun phrase is probably an offshoot of the conjunction sense (this is where it is filed in the OED entry), with the preposition for originally retaining its usual semantics (e.g., benefactive, "because of"). Early attestations of this construction in the BYU Corpus of Historical English (COHA) have for with one of its usual meanings. Three examples from the 1810's are given below.

The first example juxtaposes, cases of impeachment and [cases] for treason and murder; while in second example, for means because of. In the third example, however, does not contribute any meaning (as in almost all modern examples).

1817 The governor of New York may pardon in all cases, even in those of impeachment, except for treason and murder
1818 George Webb, of whom we would know nothing except for Franklin, who has preserved his name...
1815 Although the dialogue is not translated with literal exactness, it is faithfully rendered except for some condensation, especially in the longer speeches.

Now the OP calls attention to the fact that both "except" and "except for" can mean the same thing when followed by a noun phrase. This is because two distinct constructions involving except (preposition and conjunction) eventually converged to have the same meaning. One of these constructions (conjunction sense) allowed for flexible placement of the phrase containing except, while the other didn't. This is why you usually don't see except + [Noun Phrase] sentence-initially, but you do see except for + [Noun Phrase]. This isn't an absolute rule, but it's a strong tendency. The answer to the OP's exact question is "usually not, but sometimes."

One final thing to mention is that you will see plenty of examples of except at the beginning of a sentence, where the next word is not for. These are examples of the conjunction sense where the complement is something other than for + NP. Some examples from the BYU Corpus of Contemporary American English:

Except among Mormons, Romney doesn't do well with Republican voters who say a candidate
Except on rare occasions, appendixes are not acceptable.
Except when expressible in an individual apercu, thought is seldom self-contained.
Except where the studies explicitly address at least some of the costs of enrollment, the...
Except where noted, the sample size for men was n = 17827; for women
Except at sublime irrational moments, film is detached from true experience.