Get a piercing
Avoid the tourist spots of Camden and piercing in stores, or anyone who uses a gun.
There are places in central London, and many are very good but they are expensive because of rents etc.
Find a small, independent shop with an experienced piercer who will understand your needs and do something special.
We love London Blue Lady, (Angel station and a short walk) who also do tattoos. Tattoos need an appointment, piercings usually do not (true at most places actually but not all).
Our original choice for rooftop bar closed in the few weeks between writing the entry and publishing it. If you intend to go somewhere, double check it still exists!!