Don't want to rain on the parade, but personally I wouldn't want to join a group ride on Corstorphine Hill. Its clear the influence/damage that bikes have had on the hill since access was granted under the LRA, and the majority of walkers I've met up there have usually given me The Eye, indicating that they're still not happy about us being there. I don't mind going for a muckabout on my own when its quiet, or with one or two folk, but group rides are likely to cause more damage (especially just now) and piss off locals.
Unfortunately with the Pentlands in a dire state, there's little other quality riding 🙁 The Braid Burn Valley behind Blackford Hill has some nice stuff, but again pretty limited. I'd be interested in TJ's stuff that he's found along from Leith though.
I think I'll be doing most of my riding from now 'til Spring on my own or with only a few people to minimise my impact on the trails around Edinburgh. Might even take up a bit of road riding, if I get desperate enough!
See ya'll after Easter!