[Sundae]

Funnily enough, in conversation beer is now generally assumed to be lager - bitter needs to be specified.
"Coming for a few beers after work?"
"I'm just going to sit in the back garden and have a few cold beers."

But it's still true that if you go into a pub and ask for a pint of beer you will either have it queried (by a good barmaid) or get a pint of bitter. In fact any decent pub should query it as they will have more than one type of bitter anyway.

I noticed something similar in Leicester. The local use of cob meant a white crusty bread roll. But in general terms a cob was any bread roll. When I worked in the bakery I always checked whether someone asking for a bacon cob really wanted a bacon bap (soft bread roll). Not being pedantic - I learned in my first week that people got quite cross if you got it "wrong".

Oh, ditto rum.
Rum & Coke could mean Bacardi or Captain Morgan, but you were always in the wrong if you didn't pour what the customer expected!

What an imprecise language British English is...