It's the 'interesting rocks' place on my doorstep... but there's so many in the UK. We've got about as big a range in as small an area as anywhere in the world. There must be some good places nearer you in the Peaks but that's not my stamping ground.
If you go to that area, the river near the bridge at Kirby Lonsdale is supposed to have good corals - not seen them myself, DH has. (he used to go on geology walks, but as he bored DD with them maybe those aren't what you need)
If you like limestone pavements, there's the obvious at Malham, but more to the west - 'the limestone link' - Gaitbarrows in the silverdale area (good for flora/butterflies too). The coast there is pretty interesting - belamites to be picked up on parts of the shore and corals in the rocks. Its a nice little corner with lots of footpaths that most people shoot past on their way to the Lakes.