I echo this, make sure you get the polarity right and dont short it. It is a permenent live on one feed and selective earth on the other. Dont be fooled into thinking it is selective live. I beleive if you test it using LEDs you should be safe as they only work when in correct polarity, but dont quote me on that. My dome light went and took out the BCM, fortunately the warrenty took the hit, to the tune of £500+ for the BCM and £150 for the dome light
my warranty is also taking said hit personally i am going to wire it via a relay to run an entirely new circuit, that way i can play safe as theres a number of things that will run from it remember kids, always use protection