PCPartPicker part list:
http://uk.pcpartpicker.com/p/mYdYQ7
Price breakdown by merchant: http://uk.pcpartpicker.com/p/mYdYQ7/by_merchant/
CPU: Intel Pentium G3258 3.2GHz Dual-Core Processor (£47.99 @ Aria PC)
Motherboard: ASRock H81 Pro BTC ATX LGA1150 Motherboard (£29.99 @ Aria PC)
Memory: Kingston HyperX T1 8GB (2 x 4GB) DDR3-1600 Memory (£38.37 @ PC World Business)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£35.94 @ Aria PC)
Video Card: Sapphire Radeon R7 260X 2GB Video Card (£85.00 @ Amazon UK)
Case: NZXT Source 210 (White) ATX Mid Tower Case (£31.18 @ Scan.co.uk)
Power Supply: XFX ProSeries 450W 80+ Bronze Certified ATX Power Supply (£35.00 @ Ebuyer)
Optical Drive: Lite-On iHDS118-04 DVD/CD Drive (£9.58 @ Scan.co.uk)
Total: £313.05
Prices include shipping, taxes, and discounts when available