Welcome, I'm in North Hampshire but 'she who must be obeyed' is around Epsom Downs, so I run sometimes over her way. Leith Hill is quite a fun place, it has a small quarry, not a huge amount of rock but some, and some fun climbs etc.
As for groups, when the madness has abated I'm sure the London Scale Trail Runners will be back to their monthly meets - they have a Farcebook so you can keep up to date on their status.
Hopefully when the madness is done we'll have a chance to get out for some good times.