This is the spec I am currently looking at:   
3XS Smart - Intel Core i5 3570K - Overclocked to 4.5Ghz - Updated April 2013 
LN1198**Operating System Not required* (System Tested under Win 7 HP) 
LN46908*2GB EVGA GTX 660 Superclocked, 28nm, 6008MHz GDDR5, GPU 1046MHz, Boost 1111MHz, Cores 960 +Free to Play Bundle 
LN43592*3XS No Power Supply Required 
LN45491*3XS OCB Z77 Smart - Intel Core i5 3570K 
LN47046*3XS Systems ONLY - MSI Z77A-G45 MoBo 
LN45114*3XS-EXTREME-OVERCLOCKING- Check Build 
LN47571*2 x 4GB Corsair 3XS Only Vengeance LP Black 1600Mhz C9 Module 
LN37177*Arctic Cooling Freezer 13 CPU Cooler Intel 775/1155/1156/1366 AMD 939/AM2/AM2+/AM3/AM3+ 
LN42829*Intel Core i5 3570K,1155, Ivy Bridge, Quad Core, 3.4GHz, 5 GT/s DMI, 650MHz GPU, 6MB Smart Cache, 34x Ratio, 77W, Retail 
LN41202*Scan Overclocked Bundle Range 
£556       
Antec Three Hundred Two Black Mid Tower Performance Gaming Case w/o PSU  £61.56     
240GB Corsair Neutron Series, 2.5" LAMD SSD, Sync NAND, Read 555MB/s, Write 370MB/s, 90,000 IOPS Max 
£170.69   
2TB Seagate ST2000DM001 Barracuda 7200.14 SATA 3 6GB/s 7200rpm 64MB Cache 8ms OEM NCQ 
£68.64   
600W Corsair 2013 Edition GS CP-9020063-UK, 85% Eff', 80 PLUS Bronze, SLI/CrossFire, EPS 12V, Quiet Fan, ATX v2.3 PSU 
£64.32   
Comes to a total of £932.81.  I would like to reduce this but am unsure of what I can realistically change without too much compromise in performance.   
What do you think?