I'd second Calderdale, there's some great riding from Hebden Bridge, there's 3 or 4 trains an hour on a Saturday from Leeds for about £4 return. Most stuff marked on the OS map as bridleway is rideable and enjoyable. Along the canal towards Tod, then up to Mytholm and onto bridleway that is signposted 'Jack Bridge' hang a right where the path splits after a mile, and then steeply up past Lumnb Bank to road at Slack, short road bit into cobbled Heptonstall, then take a left past the Cross Inn, for an interesting descent that if you follow it all the way down takes you to the Blue Pig in Midgehole, Hardcastle Crags, is fairly technical in places, trees, small drop-offs, and good fun. Then you can climb out of Hardcastle Crags on bridleway and have loads of options once you get up the long hill – if you wanted a longer day I'd recommend heading left through Shackelton until you eventually come out on the road near Widdop, head along Widdop on bw and up the steep hill (bike-able) then there's a great long descent which is fast but has plenty of interest. Loads of ways to circle back to Hebden from there (but do avoid the track marked on the map by the windfarms on the long causeway that contours the hill before switching back down into Portsmouth, it's basically a bog and no fun at all).
Anyway lots of options.
