I should probably mention first of all that I personally advise against buying from CEX online, as they are bloody useless. They take ages to dispatch, have poor customer service and are a nightmare if there's any issues. That said, many people use them without issue.
I would recommend buying in-store as this is the much more reliable option. Now obviously CEX comes with the stigma of 'oh it'll be in a right state', but I'm less inclined to accept that these days. You pick the case you want off the shelf and you can inspect the disc before you buy it, so you only get diddled if you let yourself. Also, I think they use disc repairers these days anyway. That aside, the game is only a few weeks old- how bad could it be???http://uk.webuy.com/product.php?sku=885370164114
If you know of a cheaper price, post it!