Body Art
http://www.bodyartforms.com/ - Large selection at most sizes, does post to the UK and others, but does not offer insurance on non-US post which is a shame as the US postal service DOES offer international insurance.
http://www.bodyjewelleryshop.com/ - UK based, I've had some probles with getting things on time, and when they were on time the item was flawed. However they were fast to fix the flawed item, but my first order is still a sting as they wont tell me why I ordered before the next day deadline and still did not get the next day shipping I paid for. Instead they shipped it on the day it should have arrived. They have most standard sizes, but most of their bars and other things don't come in larger gauges. I would use them again, but not if I needed something ASAP or larger gauge.
ATTENTION: This website is under construction, so many things will not work. I don't have an estimated time for going live at the moment. Thank you for your understanding.
