Hi, I joined this group in Summer and we're really happy! So far we've done lots of stuff and made some good friends with other single parent families too! The group is very active and there are families from all areas of London, with kids of all ages.
Here's the link: www.meetup.com/The-London-Single-Parents-Group/
One thing though, there is a minimum fee of £5 per year to cover the group's costs on meetup (before, the mum who started it was facing the costs on her own, but we all decided to chip in).