Not great. I think it depends on who you get as to whether you receive a decent gel manicure or not. I had my manicure on Friday and it's already been coming off since yesterday. 4 days.... not good.
I recommend Splash as the only place in London to get a hot wax. I've tried a lot of alternatives and now travel across town from East London to come here.
The service is top notch and the salon is spotless. Go here with no fears as to what you're getting: they are pros.