Choices UK have COD4 Game of the Year Edition for PS3 at £24.99. There is a £1.99 delivery charge for orders under £25, however orders over £25 are free.
I tried to find the cheapest item (in stock) they have to take it over £25 and found this:
Disney Hotshots - Winnie The Pooh (CDRom) (dvd)http://www.choicesuk.com/Product.aspx//GAME_Home/PC_GAME_Home!822529
Product Number: 822529
Bringing the total to £25.98 delivered with an extra item that some of you with kids might find useful. I think that this is the cheapest for the GOTY edition even with the filler item