There was (in 2007) a tour that I took at Christ Church College in Oxford.
http://www.chch.ox.ac.uk/plan-your-visit/talks-and-tours
We did this tour more for the Alice in Wonderland connection with Lewis Carroll. (He was a math professor there and was obsessed with the Dean's daughter Alice and wrote those books for her). That was the focus of our private tour which was AWESOME! It was just 3 of us and maybe cost 75 pounds for all three of us with a private tour guide. I didn't realize until we got there that there are many HP references and much of the movie sets were themed based upon areas at Christ Church College. A lot of time has passed but that tour may have been my favorite part of that whole trip to England.