Well, I never did hear anything from anyone, as other SE Londoners on this site know, so I am trying to set a Weekenders Group up for people in SE London. I hope it will be for all parents who for whatever reason cannot get to the weekday activities organised locally (whether or not they work outside the home). I placed a message on the noticeboard section of mumsnet which has my e-mail address and I guess with the excellent publicity this site had in The Observer at the weekend, now might be a good time to ask members old and new to express an interest.
The sort of thing that I had in mind is already being done really well over at Crowthorne in Berkshire. Have a look at: www.working-parents.fsnet.co.uk (sorry, can't do activated links...) and see what you think.