An update a month on.
I bought a pair of the 36mm Cree Canbus LED 5w white from "xenonbulbs.co.uk at £7.95 and they arrived within 3 days.
I also bought two bulbs from Ebay "2 x 3W White CREE R2 LED Festoon Dome Bulb Lamp Light Car DC 12V 36mm ERROR FREE" supplied by "erresitible" for £3.69 which arrived all the way from China within 10days.

I fitted one from each supplier into each of the numberplate lights therefore testing both suppliers' products at the same time.
One bulb from xenonbulbs.co.uk failed within 10 minutes and this was eventually replaced free off charge after some hassle and 4 days. The Ebay bulb has been fine, as has the other xenonbulbs bulb.
All the bulbs look identical, I cannot find any differences at all. I think they are the same bulbs but you pay more than double for the privilege of a UK supplier.
Both bulbs (touch wood) are working fine  2002 4.4 V8 with LPG
Zambezi silver