What is the opposite of Americanize?
If someone "corrects" your British spelling, they are said to be "Americanising" - or should that be "Americanizing"? ;) - your post. What is the opposite situation called (i.e. American --> British)? Anglicising? Britainising? Australianising?
I would automatically opt for "Anglicise", but that usually implies morphing a word from another language (most logically French or another European language) to make it "compatible" with English. I can't think of an example off the top of my head though.
Solution 1:
"Britishize" and "Briticize" both are used, but neither seems extremely well established
There doesn't seem to be any verb meaning "convert to British English spelling" that is as common or well-established as Americanize/ise. Google search shows numerous examples of people using "Britishize/ise" and "Briticize/ise", although these words are mostly not recorded in dictionaries (something that many people attach some importance to, although dictionaries are not actually meant to be used as arbitrators of what is and isn't a word).
On the other hand, the apparently analogously formed nouns Britishism and Briticism, counterparts to Americanism, are common enough to have entries in many dictionaries.
And while neither of the verbs has an entry in the OED as of yet, that dictionary does record Briticization/isation which is quite similar.
I don't have any good data about how "Britishize" and "Briticize" compare to each other. The one that first came to my mind was "Briticize," but I don't know how typical that experience is.
I can't think of any other plausible candidates
"Anglicize" seems far too ambiguous to me due to its use in reference to the English language in all its forms.
There aren't a huge number of synonyms for "Britain" or "British English", and I can't think of any that seems suitable as the base for a verb:
"Commonwealth English" is a term that is sometimes used, but I don't see any comfortable way of turning it into a verb. Anyway, something like "Commonwealthize" would also be ambiguous since "Commonwealth" also refers to a generic type of political entity.
There's the "United Kingdom" or "UK", but "UKize" sounds as bad to me as "Usonian" and other adjectives people have tried to coin based on US/USA to replace "American", and I expect it would have about as much success.
There's "Albion", but that's mainly used in tongue-in-cheek references to "perfidious Albion," and I don't much like the sound of "Albionize" anyway.
Solution 2:
For converting a spelling to the UK standard, I believe you could use the word Anglify. From Oxford Dictionaries:
VERB
with object To make English (or British) in character; to put into English form.
This definition isn't far off from the definition of anglicise, but I think anglicise is so dominant for converting foreign words to English that Anglify could be easily distinguished in the realm of language.
This definition is, incidentally, identical to the one in the Oxford English Dictionary; that resource is, unfortunately, behind a paywall1, but a couple of its attestations are particularly pertinent:
1922 Times 6 Dec. 15/5 Ex-Service men going out under official auspices..are bound to succeed so long as they realize that..they must Australianize themselves and not try to Anglify their fellows.
2003 Daily Record (Glasgow) (Nexis) 28 July 15 So why do Scots feel we have to Anglify our accent all the time?
("Anglify, v." OED Online. Oxford University Press, March 2017.)
The first of these suggests an appropriate term for converting to an Australian spelling, and the second shows that the term can be used to distinguish dialects within the anglophone world.
1 If you don't have access to the OED, you might try checking with your local library; many have subscriptions to this fabulous resource, which members can access from home.
Solution 3:
Englishise (also spelled Englishize)
1 To make English in manner or in language: ‘the Englishised Indian’ (Blackwood's Magazine, 1922). Source: Concise Oxford Companion to the English Language
Ostensibly, to "make English"could also infer spelling e.g. The American English spelling aluminum would be Englishise to aluminium (British English).
Englishing
The action or process of "English"; an instance of this.
Oxford Living Dictionaries