I would have happily volunteered to take you out, but I’m away on hols. There are a couple of permissive bridleways around the Roaches and Gradbach and – within riding distance of that – some great, rocky off-road around 3 Shires Head. That’s all doable from Leek, but the first few miles will be on road. If you want some insight into the Roaches stuff, check out Peak District MTB and have a look at their proposals for developing MTB at the Roaches. It includes some maps of the ROW and the proposed ROW.
Sadly there’s not many good off-road rights of way from Leek itself, but that are plenty of canals and old railways to explore if you really do want to bimble.