After constant washing and combing, washing and combing, I finally found a solution and want to share it.
The NITTY GRITTY comb!
It's fab! Just a strong metal nit comb, each tooth has spirals to trap eggs and lice. No chemicals, no electric shocks, just wet combing and they're all gone. Obviously I'm still combing frequently to keep them away but for the first time in years we are a nit free house and all for under £12.
I don't work for the nitty gritty people, just a very happy mummy 