Just been researching as I will need some of this soon.
B&Q's 2 for 1 offer works out cheaper according to my calculator, as he
roll price is about half that of Wickes to start with:

http://www.diy.com/diy/jsp/bq/nav.js...01206 1107531
£1.76/m2
http://www.diy.com/diy/jsp/bq/nav.js...01206 1819380
£1.00/m2

mark

Agree ... B&Q cheaper.

Ash