Beer worth trying is regional (cask ale doesn't travel very far), so there's little point in reeling off a bunch of Northern pale and golden ales on the assumption that you're down London way somewhere.

"Warm" is obviously a subjective description. Ale doesn't have to be ice cold - many of them actually taste better if they're just cool, not freezing your nuts off. That said, if it's not got a bit of coolness to it, it won't be great. And if it feels warm enough that it could've been poured directly from the bladder, then it'll be unpleasant and needs returning.