Anyone know where to go in the Peak District?

Depends how tough you want it.

You could go and do the Cut Gate trail now before autumn sets in properly and you won't be able to ride it anymore (it goes from Ladybower to Langsett, then you just turn round and come back- but leave plenty of time for it, and there's no bailout route)

If you want to take it quite easy, then a nice loop round ladybower would be good- start at the visitor centre, and go round the east side of the reservoir to Derwent Edge- it's a fun descent that comes out at the Ladybower Inn. Then follow the road back along over the viaduct, then back along the west side of the lake before going up a steep rocky climb on your left by a car park. That's screaming mile, and then you can come back down the descent that comes out next to Derwent Reservoir and you can head back to the car park from there.

A lot of the classics are based out of Hope or Castleton. You can go up Mam Tor on the broken road, down it to the valley that links castleton/hope to Edale, then head back up to Hope Cross to go down the Roman Road, or up Mam Tor again to do Cavedale (be prepared for cavedale- it's tough). From Hope Cross you can also go down The Beast, which goes down to Snake Pass, but you can turn off on a track before the bottom and follow it back round to Hope.

A map will make all that make a lot more sense! Hope that helps.