Best bet is to try the BBC themselves, email [email protected]
be well polite and praise them for their help of they do a good job. (ull find it useful in the future) try and watch to see the ad again, and write down a time and date, and if u can write down what programmes it came between, they should help you!!
apparently 1xtra wont release a track listing of the trailer - coz they'll be running a competition soon where you gotta guess the tracks... that's heard from 1xtra themselves.