Unfortunately with GPU3 it seems the more you have the lower each individual card performs.
They are also probably quoting un-overclocked speeds.
I would expect them to get around 11K per card with 4 going at the same time and a slight overclock, with that CPU. So maybe 43-44K
I'd probably go for:
Intel i7 970, S1366, Gulftown Six Core, 3.2 GHz - £671.12
Gigabyte GA-X58-USB3 - £123.23
3GB (3x1GB) Corsair Dominator, DDR3 PC3-12800 (1600), CAS 8-8-8-24, DHX, XMP, 1.65V - £65.24
OCZ ModXStream Pro 600w Silent SLI Certified Modular Power Supply £67.99
Titan Fenrir Evo CPU Cooler (Socket LGA775/LGA1156/LGA1366/AMD K8/AM2/AM2+/AM3) £35.99
160GB Seagate ST3160318AS 7200RPM 8MB SATA £27.48
MSI GeForce 8400GS 512MB DDR2 PCI-Express Graphics Card - £23.49
Total: £1014.54
Much easier on the pocket when the power bill arrives and cooler too
Roughly the same PPD depending on WU.