I travel to England 3-4 times each year and one thing I absolutely LOVE about that little island are their beers and pubs.
There's just no equivalent experience in the US...which is a bummer.
In general I prefer the northern England bitters which are harder to find in the US for some reason.
Some of my favourites:
John Smith's bitter (it doesn't travel well AT ALL though)
Worthington's bitter
Old Peculier
John Courage
Many of the Brits I work with seem to like Boddington's.
Also try Strongbow or Blackthorn ciders if you can find them. They're nothing at all like sweet American ciders and have a very crisp refreshing flavor. Strongbow is a little easier to find and isn't as dry.
Probably the most depressing sight...I was out on a Friday night in Hull and in the bars all the young kids were standing around with Budweisers and alcopops. Just sad.
-Observer
Edit to add: I usually prefer to drink them refrigerated and/or cooled. In my experience most of the draught at pubs comes out refrigerated (not ice cold but definitely not room temperature). Room temperature beer doesn't taste very good to me.
All this talk of beer has made me thirsty, one Strongbow coming up.