There is a nice Can You Brew It that covers Fullers ESB, including an interview with John Keeting.
In the Sept/Oct 2008 Zymurgy John Keeting has an article on "Extra Special Bitter"
The grain bill is 95% Pale Ale, 5% crystal, and a little chocolate malt for color (yeah that does not equal 100%).
Hops were Target in the boil early, Northdown and Challanger late in the boil. Golding and Target in the fermenters, Goldings in the maturation tanks, and Goldings are added as dry hops in the cask. The time we toured through the cask line, the guide said that Chiswick got 4 plugs (2 oz) in the cask, Pride none, and ESB got 6 plugs (3 Oz!).
They use London tap water, and add gypsum to get the Ca up to about 100 ppm.
One comment on crystal malt in British Bitter. You will see recipes with 0% to a butt load looking through the Camra recipe books. I think it depends on the brewer, and what they want the beer to be. Some also would use invert 2 or 3 to add color, IIRC. Too tired to go hunt those books down tonight, or Ron Pattinson's book with more historic recipes that would contain less crystal.