i missed posting this a couple days back, but j.ko linked to this wonderful pub etiquette guide which i've been skimming thru since i came across it. below is an example of the brilliant little tidbits of knowledge it dispenses.
most natives will not able to explain the british rules with any degree of clarity. indeed, many a native will deny that there are any rules, insisting that everyone drinks what they like in britain and that he drinks pints of lager only because it is thirst-quenching and he happens to like the taste (just as teenagers claim that they wear the latest street-fashion item because it is comfortable). you don’t have to believe him. the fact is that choice of beverage is rarely a simple matter of personal taste.