there is a guy who sells it down Nottingham Lace Market, he will trim it to size and supplies various thicknesses - unfortunately I don't know his name! @Dicky do you happen to know this guy?
cant recall off hand but ive used him and he was about the same price for decent stuff as the crap stuff on - line . will have a look for his details.
@Lardy has some for sale, not a full set but enough to save you a few quid... Well he did and was surprised it wasn't snapped up as it was proper cheap too! Edit: Here's a link to his for sale advert, http://www.thelatebay.com/index.php?threads/bed-foam-£10.29263/