Do brides in church weddings go up the aisle toward the altar or down the aisle toward the altar?

Nigel Rees, The Cassell Dictionary of Word and Phrase Origins (1987) has this entry regarding the question "WHY DO WE SAY ... BRIDES GO UP THE AISLE?"

Sir Thomas Bazley fired off a letter to The Times in July 1986: "Sir, You report that Miss Sarah Ferguson will go up the aisle to the strains of Elgar's 'Imperial March'. Hitherto, brides have always gone up the nave. Yours faithfully ..."

Quite right, of course. The nave is the main route from the west door of a church to the chancel and altar; the aisles are the parallel routes at the sides of a church, separated from the nave by pillars.

Nevertheless, the phrase 'up the aisle' in connection with weddings holds strong. Could it be that the assonance of the 'i' sound in 'bride' and 'aisle' has something to do with people preferring the inaccurate to the accurate?

But I'm less concerned about the question of aisle versus nave than with the question of up versus down. Rees's discussion surprised me because he takes for granted that brides go up (not down) the aisle to the altar. There are certainly published examples where this direction is identified. For example, from Lady Helen Forbes, It's a Way They Have in the Army (1905):

The brides always look "handsome," or at least "charming," before the ceremony, and "radiant" after it ; and there is something especially touching in the "bevy" of beautiful young creatures who follow her up the aisle (each, of course, hoping it may be the last time that she will have to play second fiddle instead of first at a wedding, and wishing that it were true that one marriage always leads to others). The bride "leans on the arm of her father," she never drags him up the aisle out of step; and the bridegroom "makes his responses in a manly voice," but does not mumble them haltingly after the clergyman.

All my life, I've understood that the bride walks down the aisle to be married. Not surprisingly, there are examples in support of this direction, as well. For example, from Nancy Piccone, Your Wedding: A Complete Guide to Planning and Enjoying It (1982) [combined snippets]:

The bride must decide whether to take her father's left or right arm; if she takes his right, he will not have to cross behind her to return to his pew on the left side of the church, and this will facilitate matters. However, the bride may ask both of her parents to escort her *****, one on each side. Or the bride and groom may decide to walk down the aisle hand in hand. If the bride's father is deceased, she may ask an uncle, her brother, a close relative, or her mother to accompany her down the aisle.

And from Charlotte Ford, Etiquette: Charlotte Ford's Guide to Modern Manners (1988) [combined snippets]:

The Processional

In a formal wedding, the bride walks down the aisle on the arm of her father (if the bride's father is dead, she may choose her brother, a favorite uncle, or a close family friend to walk with her down the aisle), preceded by her flower girl or ring bearer. The maid or matron of honor precedes the flower girl, and the bridesmaids and ushers lead the processional. The bride meets the groom, the best man, and the clergyman, who have appeared as if by magic at the front of the church.

Of course, if you walk up the aisle to get to the altar, you presumably have to walk down the aisle to leave the church as a newlywed. And vice versa if you've walked down the aisle on your way in.

My questions are:

1. Is there a split in idiomatic preference between British English on the one hand (favoring "up the aisle") and U.S. English on the other (favoring "down the aisle")?

2. Has there been any general shift in recent years toward favoring "down the aisle" over "up the aisle" (or vice versa), regardless of which type of English we're talking about?

3. Which idiom is older in this particular sense—"up the aisle" or "down the aisle"?

4. Which is the more common idiom today for describing brides heading toward the alter?

The estimated results from Google Books are remarkably similar...

up the aisle to the altar - about 11,200 results
down the aisle to the altar - about 11,800 results

...but I think there's evidence of a slight US/UK split here. Americans invariably use toward where Brits use towards, so I think these results for AmE usage are significant...

up the aisle toward the altar - about 830 results
down the aisle toward the altar - about 1,700 results

The typical BrE versions of this form show no such preference...

up the aisle towards the altar - about 450 results
down the aisle towards the altar - about 423 results

As mentioned by others, there's also evidence from NGrams that both prepositions were equally popular until about a century ago, since when down has become increasingly preferred. If you check the AmE and BrE corpuses in that link, you'll see this usage shift is much more apparent in the former.

I wouldn't like to say what percentage of those results could reasonably be called "idiomatic" (i.e. - "When are you going to take her up/down the aisle?" = "When are you going to marry her?"), but I'd guess that wouldn't often apply to any versions involving ...toward/s the altar.

Personally I've no particular preference for either version (whether used idiomatically/figuratively or literally). It's no different to "He lives just up/down the road from me", which I see as freely interchangeable in contexts where there's no obvious change in "elevation above sea level" between our two houses.

There is a marked preference for down the aisle. See this ngram: (bride up the aisle),(bride down the aisle)

I get zero hits for 'bride up the aisle' in British English.

I'm thinking of the phrases "walked|accompanied|brought|took the bride ___ the aisle".

And there's a marked preference for down the aisle generally: * the aisle.

According to Ngram, "down the aisle" passed "up the aisle" in frequency of usage in the 1890s. Since then, usage of "up the aisle" has actually increased somewhat, but usage of "down the aisle" has increased more than fourfold.

Of course, I have no idea what proportion of these mentions had to do with brides, nor to what extent Google Books's corpus might favor American sources over British.

Sorry I'm so late to the conversation.

The bride walks UP the aisle with her father, because the altar is viewed as the place of the presence of the LORD. God is always on higher ground than we are. Such a meeting place between God and man where major covenants take place is typically a mountaintop. (Moses at Sinai, Abraham at Moriah, Jesus at Jerusalem)

Because the marriage covenant includes God as the ultimate initiator, protector, witness, and judge of the couple, they stand before him to take their vows and receive his blessing. Hence, they have traveled up the mountain into his presence, and walk DOWN together. Throughout the course of their marriage, they may periodically point to their vows as the "high road" to stick to, never the "low road."

Many of the reasons why we do the things we do have been forgotten.

It may be that "down the aisle" has taken the lead because "up" anything can be construed as rude. We live in a time where profanity is much more common and socially acceptable, and therefore, if you say "up" something, people aren't sure if you're attempting a double entendre. (Or, not... but it makes sense to me.) (US)