I had the same problem with a No 5 recently and patched the draws to fit it correctly. There is an article in Peter Laidler's list of articles which very precisely describes the method used to "re-fit" a worn stock correctly. Here's the link: "Worn draws in your No1, 4 or 5 fore-end .... " (by Peter Laidler) Also there is more information and illustrations from Ed Horton in this thread: regarding No 4 and No 5 rifle bedding - Military Surplus Collectors Forums
I've since done a couple No1's and you've got be very, very careful about the amount of adjustment you make (by fitting the draws and collar) as it is a very sensitive fit. ie. it is easy to take too much off.