Optimus III 15: http
/www.pcspecialist.co.uk/notebooks/optimusIII-15/ (essentially the same thing as the Sager NP6165)
Comes with one of the best GPUs and one of the best displays available within your budget. You might want to take a Core i3 or Core i5 CPU upgrade because the Celeron B970 receives very low benchmark scores in comparison, and you may want to take a hard drive capacity / speed upgrade. You should also bump the memory up to 4GB, because 2GB is on the low side even for basic usage (on a 64-bit OS).
15.6" 1920x1080, NVIDIA GT 650M, i5-3210M, 500GB 7200RPM = £694.00