Watch out for tourists, cyclists and camera vans in lay-bys on the A621. Arrows on bends aren't for show, quite a few tighten up. Ride anti-clockwise to get some great views on the way down to Hathersage, then turn round and ride it clockwise (cut out Hathersage and ride up through Froggat for a variation).
Lots of interesting side roads in N.E.Derbyshire so you can bypass the 50 limited A roads, but surfaces are very mixed and water run-off can drag gravel across the road.