No visit to London ever goes by without a stop at Neal's Yard Dairy. Neal's has two shops (in London I'm a fan of the Borough Market location) and I often go to taste my way through the 70-some cheeses they sources from cheesemakers in farms around Britain and Ireland. Many of the cheeses are matured in Neal's own maturing rooms in Bermondsey. The shop owners are poetic about their cheeses. Ask to try the Montgomery's Cheddar, made near Cadbury and don't miss the Cashel blue, which has an almost runny texture when ripe.
Cheese nerds can sign up for classes that range from an hour-long introduction to British Farmhouse cheese to a two-hour class on what makes cheese stinky.