OS used to do a 1:100,000 map, called "Tour Travel Map" which were absolutely perfect for cycling.1cm to 1Km (doh!) every road was on them, all the extraneous detail was stripped, they were extremely clear and covered a useful amount of territory and provided town maps, too. I still have the two I bought for DunRun back in .... (looks for date)....2006/7?
ETA - obv, no contours, which is the only major drawback.
EATA - apparently they still make a tour map, but it is a mixed scale 1:175k/100k and only for selected areas, not the whole country. Probably most use for motoring.