Smiledent on the corner of Mattison Road and Green Lanes is great and does NHS service. Been going there years and my 4 year old also likes it there.
Torrence, Seven Sisters Road. A bit further away. Check their reviews on the NHS site and on stroudgreen.org
Dentist next door to Iceland Green Lanes Harringay.
I may have been unlucky as went to Torrence based on great reviews but the dentist I have seen was clueless, missed very obvious need for 2 fillings and would not do clean within the 1st NHS band, I was told that can only be done by hygienist for a complete separate charge.
Went somewhere else, all was done with the 1st NHS tier.