Picked this up in the PC World store in Beckton, East London this afternoon - there were 3 more copies on the shelf - might be worth checking you local branch!
Cheapest I can find online is £14.89 at SendIt - http://www.sendit.com/sendit/8616179.product
This item is also included in the Buy One Get One Free offer
I know this is a limited offfer and availability will vary from branch to branch, but hopefully this might help someone else pick this game up at such a fantastic price!
Other items in the sale included:
Beautiful Katamari - £4.97
Virtua Fighter 5 - £4.97
Juiced 2 - £4.97
Conflict Denied Ops £9.97
Mass Effect £9.97
Need for Speed Prostreet £9.97
Ghost Recon 2 £9.97
Ninja Gaiden 2 - £9.97
Dead Space £19.99
Mortal Kombat vs DC Universe £24.99
All of the above are included in the BOGOF offer - there were quite a few more, but I can't remember them all, but the shelves were well stocked with all of the above