I have been searching out WTT's as I like using them when making scenarios for TS1 and I now have quite a collection, they are fascinating to read as well. However I haven't found many free online ones, there are a couple of sites. Michael Clemens has quite a collection of Western Region steam period and there is the Network Rail archive which starts around 2009. I haven't found any free ones covering the BR period even when searching. Most of mine have come from ebay or transport book sellers. I know the national archives have large collection, but they charge if you want a copy of one. I would be very interested to know of a source of BR period timetables.