Welcome to BLF! 
You are on a flashlight forum, so the solutions that many of us have for driving leds may be a bit different from what you need for your application. The electronics that we use to drive the leds are often small and simple and are low-voltage to have them run from batteries. Also we like to drive leds hard and do not care a lot about led life. Many flashlights do have thermo regulation though, not to keep them longterm happy but to prevent shortterm frying.
That said, we may have some help for you. There is not a short manual here on BLF, but there are some resources for leds and stuff, mainly this one may be of help: LEDs & Other Stuff - (Reference Guide) .
There are a few vendors that sell flashlight related parts, like leds, drivers, reflectors etc. Since you are in the UK, the US sources (mtnelectronics.com, illumn.com, Mouser, Digikey) are often too expensive because of shipping cost, others sources are kaidomain.com, banggood.com, led4power.com.