you can ride the TPT all the way into sheffield (hillsborough) altho' after greno/wharncliffe woods its not the TPT, just al ittle known trail from outibridge. We used to ride from hillsborough all the way (by passing penistone) over cutgate, derwent edge and down to bradfield for a grand day out.
The sheffield & barnsley and the dark peak 1:2500 ord survey outdoor leisure maps will be your friends.
our club has just started some mid week mtb rides departing 6pm from hunters bar, sheffield. Turnout at the moment is low, as we're really a road club.
other clubs that might suit you are barnsley road club & birdwell wheelers (again really road oriented). Try phoning cycles promotions at worsborough or "try cycling" (up huddersfield way) shops to see if they have any off road club connections
BTW, the hillclimb at huddersfield only had national status last year. The location of the "national" moves each year