Additions Direct have got Little Big Planet on their site reduced down to £27.60 as they are having a sale. If you are a new customer, you can sign up and use code ZG335 which is £10.00 off a £25.00 spend.
Unfortunately they charge £3.95 delivery but this still gives it a price of £21.55 compaired to £24.79 @ Simply Games. The item is in stock and I believe the offer ends on Sunday (23rd). When I went to place an order it said delivery would be around 6 days time.
I know the Simply Games offer is still going but stocks are limited, so if they run out and you don't mind waiting a few days for it then check it out. You can also pay by card rather than on a credit account.