What video card did the £849 i7-860 have?
Among the other 2 you linked the x6 1035t/HD 5770 option is clearly superior to the i7-860/GT 330 option. It's the video card that makes the difference.
In Passmark GPU video card benchmark testing
the cards got these scores:
GeForce GT 330 = 639
Radeon HD 5770 = 1567
That GTX 460 video card in that system AMW1011 linked is far better option for gaming, together with the i5-750 CPU.
Passmark GPU score: GeForce GTX 460 = 2214
Excellent quality parts too - Gigabyte motherboard, Corsair PSU, Evga video card.