I'm not in London (now) but I think the idea might be a good one. With the usual reservations about inviting strangers into your home.

When we were starting to go to sessions we had a family tune night (daughter, other daughter's MIL and her daughter). We learnt tunes together. After a while we found that our tune lists diverged (due to unequal talents and amounts of practise) and we went to sessions instead, but it was a good start.