There is indeed, close to Tottenham Court Road in London. http://www.gialondon.co.uk/. I do not think they offer Lab Services on site though, so it would be best to contact them.
SSEF in Basel http://www.ssef.ch is another highly reputable laboratory in Europe.
Try searching for the names "Gem and Pearl Testing Laboratory" + "Stephen Kennedy". I don't have his new address but it is somewhere in Kirby Street off Hatton Garden in London. Directory enquiries should be able to help. Good luck!