Exactly what simondbarnes said – from Rivington Barn area, head up past Yarrow Reservoir, cut down toward Knowsley Lane, into Anglezarke Res Car Park, follow the obviuos path around the Res through the horse barrier, follow all the way to the end, hit Moor Road, turn left, along the road and then a left up to Healey Nab for a play – then maybe across the farmers field to the canal alongside the M61 back toward Rivington and cut off at Cowling Brown, onto Long Lane, then Hut Lane over the Motorway, linking upto Back Lane – Some good singletrack and will keep you happy for 90mins or so
Also Abbey Village trails worth a look but maybe a bit far out