Wherabouts in the South East are you? Abridge is worth the journey, they have a great crowd and some brilliant fields.
Possibly a bit more local, Mayhem South East (separate to Mayhem Essex in Abridge) also have a walk on group that organise more or less monthly events, usually at Longfield near Dartford - facebook group is MSE Walk On Community.
There's a group of us that go to Sidcup, but not as often since we got hooked on tournament play.