In reply to toddp: I have noticed a few chalk marks on the alley that leads down the back of Waitrose, which leads me to believe someone / some people are climbing their fairly frequently. I'm not sure what the grades concerned are, but it looks hard to me.
Alternatively, in town, I know of three possible sites near where I work.
1. The wall / slab at the base of the Castle Mound / Macclesfied House. I've not climbed on it yet, but keep intending to. The wall starts out at a nice easy slabby angle and steepens up as you go around the corner.
2. The slabby butress at the base of the castle turret - around the back of the castle. About 5m high - quite a lot of sq. footage of climbing. Has the benifit of window-bars to top rope from if you so wish. The castle owners probably won't like this though... Possibly an early morning climbing location!
3. Bulwarks lane - a variety of problems, including what looks like a phenomenal finger crack... worth walking down there just for a look, I think.
Cheers,
Tim H.