You could save some here depending on how far you intend to OC. If you don't plan on going past 4.3-4.4GHz then you should be ok with the Coolermaster Hyper 212 Evo at only £25.
Anything over 8GB gives very little benefit when gaming. If this machine is purely for gaming, save some money here.
GPU (maybe...not so sure on this)
Depending on your monitor resolution you could save nearly £60 by getting the 2GB version instead of 4GB. The performance increase is supposed to be negligible on anything 1080p or less.
Thats about it really. Anything else you begin to sacrifice performance/features for the savings.
Here is what I would go with. First, the 212 EVO will give you good overclock. 16GB of RAM is overkill for gaming. The AsRock Extreme 4 is a great motherboard for the price. The 680 is way expensive compared to the 1.01GHz 670. In fact, the OC 670 will perform equal or better than the 680. 4GB of vRAM is m way much unless you are using three monitors. I added and SSD for your OS and main apps. You will appreciate the loads speeds.
Using Tom's recommendations for Gpu, the 7970 actually gets the vote over the 680. With that Ghz edition being as cheap as it is, I put that in their. Still a 3gb card too.
Agreed. Not sure why I didn't think of that myself!
And to add to it here is a quote from tomshardware themselves:
"We really like AMD's Radeon HD 7970. There's really no reason to pay extra for a similar-performing GeForce GTX 680 unless its 55 W-lower thermal ceiling is necessary"
Even better, Scan are currently doing an XFX HD 7070 for £318.
£100 saving on the GTX680!!