Yes this was a Citroen Xsara advert and it featured Claudia Schiffer walking down some stairs into the car.
The music featured in the advert is Rise by Craig Armstrong. The section of the track used in the advert is 3 min 16 seconds into it. The Craig Armstrong album you need to buy is called THE SPACE BETWEEN US, Rise being track 8 on that album. I would highly recommend this album, if you watched the first series of MacIntyre Undercover (BBC Nov 99) you will recognise the music on this great album. Hope this helps you.
http://www.absolutelyandy.com/tvadverts/