I have used a brand called iceled in my house.It is a 12v high output multicolour led product. If you go to Argos/maplins you can buy a 12v power supply for £5ish. I also used something called flexitape, it is a strip of leds in a thin waterproof jacket.It can be cut to length and uses little power. I have just bought some rgb led bars from him but they are not as light as the led tape for sticking to the back of the tv.
www.iceled.co.uk
I have a very experienced customer in sheffield who specialise in led lighting for cars called Source Sounds ( 01142571550). Speak to Lee or Paul they will look after you. They are top blokes. Tell them Pete from Celsus gave you there number.
http://www.sourcecars.com/index_new.html