Sorry if it's a bit off topic but have you considered other childcare options? I found private nurseries very expensive (state ones impossible to get a place in) so took the childminder route and was very happy with this as my children had a secure home environment rather than lots of different people looking after them and were made to feel like part of the family. They were taken to playgroups and there were usually one or two other children being cared for in the home as well. We had the same childminder for many years and, while of course not cheap - why should it be?, I think it cost less than a nursery would have. I have colleagues paying over £1000 per month per child in a nursery.
If you have space, a nanny could also be an option.
Assume you have considered these and rejected them but just thought I would mention it. Lewisham would have a list of registered childminders that you can interview.