Not a lot of hills in Northamptonshire but if you look for them there are some. In fact the “Northampton Uplands” is an official hilly ridge that runs west of Northampton.
Offroad biking isn’t well provisioned for in Northamptonshire. However there are some popular Facebook communities. The most popular are the Northampton Mountain Bike Group and the Wakerley Woods Mountain Bike group.
The former is mainly about biking at Delapre Abbey grounds and Harleston firs along with trips further afield. The latter is all about biking at Wakerley and Fineshade woods.
Woodland with off-piste trails and jumps
Wakerley / Fineshades woods
Plenty of off-piste trails but no official trail.