Hi Matty81,
Drop us an email and we will help you, send us the link to the ones on eBay and we will let you know if they are really what they claim to be.
As for the interference none of ours have this issue. We use genuine Cree LED chips which use genuine stated number of wattage output in line with BMW electronics which ensure you don't get an interference through the radio.
Our email is
Forums@HorizonLEDs.co.uk
Thanks,
Horizon LEDs