This is officially the cheapest price i've managed to find for Bioshock, which is the most intense and touted to be the best game on the Xbox 360, which is a very bold statement indeed with OXF (Official Xbox Magazine) also believing this, offering this game there first ever 10/10 review.
If you're a new customer of Softuk, then this is an unbeatable price, offering the game at £34.99 but after the 15% voucher, it then becomes £29.75 including free fast delivery.
Bare in mind that Softuk are very efficient with pre-orders with every order i've made arriving the very next morning and they normally send out pre-orders 2 days in advance, so you should receive it a day before the release date.
I don't know if many people remember as well but Softuk also managed to have stock of Mario Party 8 23 days before most other retailers in the UK, so this may be the case again.
I hope this helps. :)
EDIT: 15% off code is 'BROADBAND'