The 3 Mobile Ad is ...

[SaxyJag]

...especially since I was one of the first to ask, but:

THE MUSIC ON THE 3 MOBILE AD, WHERE THIS GIRL HAS THAT BIT OF PINK/PURPLE SATIN FOLLOWING HER AROUND IS CALLED "FORGOTTEN DREAMS" AND IT'S BY LEROY ANDERSON.

You can hear a snippet here:

http://www.leroy-anderson.com/html/hearthemusi c.htm

and you can buy it here:

http://www.amazon.co.uk/exec/obidos/ASIN/B0000 09HTO/qid=1148990250/sr=8-1/ref=pd_ka_1/026-61 31124-1116458