Browsing through the site this morning and stumbled across the Oh La La Cheri Open Back Crotchless knickers (plus size) - and WOW!!! 
http://www.lovehoney.co.uk/product.cfm?p=33419
What an ass on the model!
In a couple of the photos I genuinely thought that it may have been photoshopped,
http://d3f650ayx9w00n.cloudfront.net/940/59487-1.jpg
http://d3f650ayx9w00n.cloudfront.net/940/59489-2.jpg
but when I happened across the photo of straight on from behind - 
http://d3f650ayx9w00n.cloudfront.net/940/59489-1.jpg