There are many skills that must be mastered to successfully complete an ambitious pub crawl such as this. You need to be able to map out an efficient route, be able to navigate from one bar to the next, and be very careful with your timekeeping to keep on schedule.
There is one thing that sometimes gets overlooked when planning out these kind of adventures - The Drinks.
Having done a bit of light research on the topic of pub crawls, it seems to be that some schools of thought suggest skipping a drink here and there or maybe substituting in a soft drink for something less sugary and more beery. They also suggest skipping a few venues altogether. This might be acceptable under some codes, but the Code of Honour* that binds all alphabet pubcrawlists together will not permit such shirking of their duties. At each pub you should attempt to drink some kind of booze: a lager, a stout, an ale, a spirit, or even some wine. All of these seem reasonable. Asking for an alcopop, or some kind of pink cocktail with an umbrella in it is pushing it a bit.
How much booze to ask for is another question. From a logistical point of view you won't have more than half an hour in any one pub, so finishing a full pint in each location would be a very big challenge after the first few places (especially if you are ordering pints of cabernet sauvignon).
Ordering half pints seems like a better bet if you want to go for that continental vibe, but you might not want to end up looking too continental, if you know what I mean.
A bottle of beer seems like a good compromise, in that it takes no time to serve and can be drank relatively swiftly. Please avoid the half litre bottles of that tasty german beer. It's a lot stronger than the regular stuff we get on draft, and you will find yourself singing very early on in the evening. There are some beers from the other side of the Atlantic that are popular in bottles which may appeal to you. However, some are barely stronger than a bowl of sherry trifle so you'd really have to look into your conscience before trying to purchase one.
Spirits are a good option because they're not going to take too long to drink or serve, so allowing plenty of time to chat with your fellow alphabet pubcrawlists about how peculiar you feel after drinking that shot of tequila too quickly.
In summary the second rule is:
2 - Know your drinks*not a real Code, yet!