This is £6.29 on the UK Store but if you buy it from PSN America at the moment then you can get it for half of that price in their Spring Sale.
Great game apparently and always seems to get good reviews (8.0 on Gamespot)
You will need a US PSN account to buy this but the account is free to setup and you will just need to use the US account to buy it and start the download then you can continue the download, install and play it on your normal UK logon if you want to. My primary PSN account is for PSN USA and I sometimes buy content from the UK store and then just play it using my American account.
Visa cards don't work unfortunately but a Mastercard/PPMC/Entropay etc will all work fine.
Gravity Crash (PS3) is also the same price for those interested but I've never really heard of that.