You can buy a new lower door seal from espares.co.uk here's the link to the part I think you need, but please check the exact model number yourself.
http://www.espares.co.uk/productsearch.aspx?k=seal&c=1083&ma=856&mo=438563&sa=1
I've just replaced mine, and it took me about 30 minutes.
Steve Brough, April 2006