Tattoos

Slightly weird question, is there anywhere in London that is likely to have walk-ups available and isn't shit? A friend of mine is in town from the US, and last time I was over there we got small matching tattoos (just black ink, about the size of a 50p piece) for $40, thinking of doing the same this week...

I've not been there but Kids Love Ink in Deptford gets a regular thumbs up on this thread for walk ins. Maybe they're less busy cos they're a bit off the beaten track?