Ok so just popped in Morrisons while I was out.
Apart from a few more games cropping up in their "When it's gone, it's gone deal" which they had a load of GH WT Ps2 for £6 now. I seen Revenge of the fallen had just been reduced.
Don't know if it's the cheapest around but I thought I'd let you know.
£26.99 PS3 and 360,
EDIT: Typo (thanks Babbabooey for pointing that out LOL)
Seems like GHWT is a better deal though?