There have been cx races (with plenty of mtbs riding) all over the this autumn / winter – there is a NW league, NE league, Yorkshire etc etc so one or more races every weekend if you really wanted. The CXs have actually been really fun and friendly, with a few good mtb courses (Rossendale, South Lakes etc).
MTB races at Haigh hall in February.
Duathlons in Grizedale and Whinlatter.
Plenty of “challenge rides” (e.g. Mary Towneley Loop, Dean Barwick).
Scottish races are great and usually a few just over the border.
Sounds like there might be a race series in Whinlatter sponsored by Altura
http://www.whinlatterchallenge.co.uk/