in the US actually ...here for the best California Lightworks 200w Solarflare http://www.californialightworks.com/Products_SolarFlare.htm
from memory there is a guy in Wales, but someone replied that they were chinese knock offs, I liked the modular idea involved tho! gogle it?
You can check out the ones I am using, I think they can ship to the UK... they are called Intelligent Gro LED.
I would go to topledgrowlight.com because they seem to have the best bang for your buck. I looked at a lot of journals and youtube videos that use their lights and I have to say i am impressed. On the other hand, I have seen other places that offer stronger diodes (10w) and that is appealing as well.
agree with stillmatic, theres a topledgrowlight thread with tons of grow journals by people on this forum. I literally just ordered a mars 2 700wat from them last night not all Chinese products are bad, the grow journals proved that to me EDIT: http://forum.grasscity.com/lighting/1289197-top-led-grow-light-family.html