This is about the cheapest I could recommend: PCPartPicker part list:
http://uk.pcpartpicker.com/list/XcntQV
Price breakdown by merchant: http://uk.pcpartpicker.com/list/XcntQV/by_merchant/
CPU: Intel Core i3-6100 3.7GHz Dual-Core Processor (£92.91 @ Amazon UK)
Motherboard: MSI B150M MORTAR Micro ATX LGA1151 Motherboard (£68.78 @ CCL Computers)
Memory: Crucial 8GB (2 x 4GB) DDR4-2133 Memory (£39.99 @ Amazon UK)
Storage: Toshiba 2TB 3.5" 7200RPM Internal Hard Drive (£38.33 @ Aria PC)
Video Card: Gigabyte Radeon RX 460 4GB WINDFORCE OC Video Card (£108.90 @ CCL Computers)
Case: Cooler Master N300 ATX Mid Tower Case (£32.16 @ Amazon UK)
Power Supply: be quiet! Pure Power 9 400W 80+ Silver Certified ATX Power Supply (£49.99 @ Amazon UK)
Operating System: Microsoft Windows 10 Home OEM 64-bit (£84.98 @ Novatech)
Monitor: BenQ GW2470H 23.8" 60Hz Monitor (£100.44 @ Amazon UK)
Total: £616.48
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-11-07 16:11 GMT+0000