here you go, includes 2gigs RAM, ATi x1900gt(HIS) core 2 duo and is only a little over your budget(£7) be aware the RAM is this week only so if you dont buy it before thursday THIS week it's £30 more, or you could drop to the:
MY-034-GL GeIL 2GB (2x1GB) PC5300 667MHz Value DDR2 Dual Channel Kit (GX22GB5300DC) (MY-034-GL)
£139.99 £139.99
which is the same price as the 800Mhz set, but slightly 'worse', hope it looks alright
CA-040-AN Antec Sonata II Piano Black Quiet Case - 450W Smart Power PSU (CA-040-AN) 1
£66.99 £66.99
CP-135-IN Intel Core 2 DUO E6300 "LGA775 Allendale" 1.86GHz (1066FSB) - OEM (CP-135-IN) 1
£99.99 £99.99
MB-061-GI Gigabyte GA_965P_DS3 (Socket 775) PCI-Express DDR2 Motherboard (MB-061-GI) 1
£89.99 £89.99
GX-057-HT HIS ATI Radeon X1900 GT ICEQ 3 SILENT Heatpipe 256MB GDDR3 AVIVO TV-Out/Dual DVI (PCI-Express) - Retail (GX-057-HT) 1
£127.99 £127.99
HD-018-SA Samsung SpinPoint P SP2504C 250GB SATA-II 8MB Cache - OEM (HD-018-SA) 1
£44.99 £44.99
CD-047-LG LG GSA-H22NBAL 18x18 DVD±RW Dual Layer ReWriter (Black) (CD-047-LG) 1
£19.99 £19.99
HS-020-ZA Zalman CNPS9500-AT Aero Flower (Socket 775) CPU Cooler (HS-020-ZA) 1
£29.99 £29.99
FG-024-AK Akasa AK-183-L2B Amber Ultra Quiet 120mm Fan - 3 pin (FG-024-AK) 2
£9.95 £19.90
MY-058-GL GeIL 2GB (2x1GB) PC6400C4 800MHz Ultra Low Latency DDR2 Dual Channel Kit (GX22GB6400UDC) (MY-058-GL) 1
£139.99 £139.99
MO-049-HY Hyundai ImageQuest N91W 19" Widescreen LCD Monitor - Black (MO-049-HY) 1
£144.99 £144.99
Subtotal £784.81
Shipping (City Link Parcel Next Day (Delivered Mon-Fri)) £12.95
VAT £139.61
Total £937.37
edit: you might also want to upgrade the PSU, but mine is doing 'fine' running pretty close to the above