I would like to recommend the folk dance classes at Cecil Sharp House. My daughter has been attending for a year and we couldn't be happier! There is singing, dancing and live music played on the site. Kids have great fun and while they're at it, we parents can relax and enjoy a cup of tea and a slice of (wonderful!) cake from the cafe.
There are two groups: 4 to 5 years old and 6 to 9 y.o. Pricewise, I think they're very reasonable (especially compared to other classes). Only £50 for a whole term.
The reason why I'm posting this is because unfortunately they need more children to make the classes sustainable, or will have to stop them. There's 6 of us already, but we need at least 4 new children in the 4-5 year old group.
They're offering one free tester session per child, so nothing to lose! Come and see if your kid(s) enjoy it, I'm sure they will :)
Here's the link to their website www.efdss.org/front/c-minors/c-minors/214228/131