This is the best Build you can get for 500 pounds.
PCPartPicker part list:
http://uk.pcpartpicker.com/p/L8n4f7
Price breakdown by merchant: http://uk.pcpartpicker.com/p/L8n4f7/by_merchant/
CPU: Intel Core i5-4590 3.3GHz Quad-Core Processor (£154.92 @ Aria PC)
Motherboard: ASRock H97M PRO4 Micro ATX LGA1150 Motherboard (£68.66 @ Amazon UK)
Memory: Kingston HyperX Fury Blue 8GB (2 x 4GB) DDR3-1600 Memory (£34.97 @ Ebuyer)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£34.92 @ Aria PC)
Video Card: Gigabyte Radeon R9 380 2GB Video Card (£154.98 @ Amazon UK)
Case: Silverstone PS08B (Black) MicroATX Mid Tower Case (£30.43 @ CCL Computers)
Power Supply: XFX TS 550W 80+ Gold Certified ATX Power Supply (£37.99 @ Amazon UK)
Total: £516.87
Prices include shipping, taxes, and discounts when available