The original (A4) guidebook is now out of print!
However the new (A5) North & South Downs and Chilterns guidebooks (with their expansion packs) basically make up all of the routes that were in the South East book (with a few new routes and updates too). Get the 2 new (A5) books and their expansion packs here for a reduced price.
FREE: GPX files for all the routes, when you buy the book.