Existing Blinkbox account owners, search and buy "Shutter Island" from the Blinkbox website, and enter code "SHUTTER" when prompted before the payment screen. This code is meant to only work on the rental, but worked for me on the full, unlimited purchase, saving you £9.99.
If you don't have a Blinkbox account, search around to see if there is an offer for free credit when signing up through an affiliate before creating an account.
Nice little find, especially for those who got the £20 free credit offer, bringing us up to £30 of free goodies from this company. Films stream brilliantly through the PS3, or can be watched online or downloaded for offline play.