Well, the Beer House as mentioned by Dr John closed a while back but has since reopened though I believe it's not anywhere near as good as in it's previous existence.
The place on Swan St as per Marceldesailly is the Smithfield, which had an excellent choice of ales on my last visit. Almost opposite that is Bar Fringe with a good choice of ales and bottled beers while a little further down the road is the Crown and Kettle. All these can be passed en-route to the Marble Arch from the City centre making an excellent crawl! Be warned though, all are extremely popular so tend to get very crowded, especially at weekends.
If prepared to travel a little further afield, then the New Oxford and the Crescent, both in Salford, are well worth the effort.
