Hi All,
This tip came from XM-L. Bells Autospares in Bishops Auckland (http://www.bellsautospares.co.uk or Tel: 01388-609590) apparently have 12 Series I & II XM's that are going to be crushed soon because they're short of space.
I called them today and got 2 front window mechanisms (including an anti-pinch unit) - so there seem to be some good spares available.
Roy