Sorry, I should have mentioned that as well.
Yes I have downgraded to 341.92, and Yes that does solve the Pixelation issue. I am running that currently. Thanks Dave.
Interestingly however, before I noticed the problem I was using 354.13 without issue. (I also tried to revert back to that version but the problem is with that driver too now.)
Whilst I had several driver on my Download folder, i though to try the "Culling" solution.... Albeit unsuccessfully.
FYI, NVidia have released updated driver version 362.56 that should contain a fix for this issue:
Win8 and Win7http://www.nvidia.com/download/driverResults.aspx/102689/en-us