I searched a bit and cannot find a single dealer who supply Depo xenon headlights in UK. I guess the demand is very poor. We people like to stick to original headlights or at least original upgrades to Xenon or LCIs.
You can try USA, but they are around $650 and LHD.
There are some chinese stuff on ebay and they cost around 300-360£ and again no surity.
Germany, about £240 pounds (turning signals non-leds, yellowish angel eye lights which cannot be changed) and they are also LHD.
Not an easy task, spent 40 minutes on searching most of the websites.
If you come across something good, feel free to share with us.