I had my eyebrows threaded and tinted and was really happy with the result. I'm always cautious when it comes to my brows after too many horror experiences but the staff were really knowledgeable and talked me through every step to make sure I was happy. It's not the cheapest but I'd definitely recommend.
I have been to Pure Wax London a couple of times now. I've always been happy with the experience, I have had different therapists and they all have the same standard. I always find them friendly and efficient. FYI - You need to walk through the downstairs tourist shop to get to the upstairs.