Ultimately this would be ideal!
PCPartPicker part list:
http://uk.pcpartpicker.com/list/DbZ6XH
Price breakdown by merchant: http://uk.pcpartpicker.com/list/DbZ6XH/by_merchant/
CPU: Intel Core i3-6300 3.8GHz Dual-Core Processor (£119.99 @ Novatech)
Motherboard: ASRock H170A-X1/3.1 ATX LGA1151 Motherboard (£71.71 @ CCL Computers)
Memory: Crucial 8GB (2 x 4GB) DDR4-2133 Memory (£25.76 @ Amazon UK)
Storage: A-Data Premier SP550 240GB 2.5" Solid State Drive (£47.99 @ Novatech)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive (£41.99 @ Amazon UK)
Video Card: Sapphire Radeon RX 470 4GB Video Card (£149.00)
Case: Deepcool TESSERACT BF ATX Mid Tower Case (£24.99 @ Ebuyer)
Power Supply: EVGA 500W 80+ Certified ATX Power Supply (£39.95 @ Overclockers.co.uk)
Total: £521.38
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-07-05 19:39 BST+0100
I know it's a bit over the budget but you shouldnt cut on those, such as SSD and VGA, unless basic basic gaming which you should be fine with worst VGA.I edited to have the RX470, which should be announced later this month.