Best: Hogs Back Bitter (Hogs Back Brewery), I discovered this one at university, unfortunately they only really supply this one to pubs in the near vicinity and don't sell it by the bottle. If my wife and I are hosting a party I'll invariably make the 80 minute round trip to pick up a mini-pin though.
Preferred tipples available in most supermarkets and some bars: Tanglefoot (Badger Brewery), Hobgoblin (Wychwood Brewery - although this can be hit and miss), Courage Directors
Favoured beer available more or less everywhere (except clubs apparently, there I have to go for spirits): Guinness