You can get a book on best universities in uk, one is by virgin, and one by 'the times' Uk, just ask in easons, the architecture section will only be 2 pages, so pick it up in easons and read it (don't buy it an leave) it will list off university league table 1st 2nd 3rd etc.
But consider different books have different tables, nottingham was top on one, while cambridge is top on another. also someone mentioned the mack in glasgow that has a very bad rep in those books, but is supposably quite good, I think AA is not suitable for people coming st8 out of school. But double check all these things as they are just things i've heard rather than researched.
Note Cambridge school of architecture is closing down to the best of my knowlegde.