Not sure if they will honer the order but here goes:
Sign up as a new customer (if your are already a customer just use a new email address to sign up).
This will give you £15 off your first order (Code ZZ551).
Search for Gran Turismo 5
Add it to you basket
At the bottom of the checkout page you can enter some codes... these are:
ZZ551 - £15 off your order (if not already there)
ZZ018 - £20 off your order
Then all you have to pay is delivery of £3.95!!!
As I stated at the start of the post, they may decline the order once reviewed but its worth a shot :-p