If you ride up the ashton canal to portland basin and hang a right under the stone footbridge..you'll find yourself on the peak forest canal, this will provide you with a further 12/15 mile run out thru marple locks eventually terminating around whaley bridge. If you're feeling lively you can jump out onto the road (Whaley end) and the appropriately named Long Hill will be infront of you, up there 7 mile and you'll be in buxton, where with a little help from a sane local you should be able to locate the Tissington trail which interlinks enough to provide plent of mileage with breathtakng scenery
Grab yourself a pair of semi slick style of tyres if you're not going fully dedicated Mountain bouncy forky, sometimes life's not just so convienent to provide all off-road on your doorstep but with a little swerve (tyres) you can tie two or three trail types together via a bit of road.
Rochdale canal out of town is rideable thru to rochdale, Tod, Ebden and Sowerby bridge, Hudderfield, dropping down into Marsden, saddleworth, staley rowing boats, portland Basin, etihad.