PCPartPicker part list:
http://uk.pcpartpicker.com/p/K9sRt6
Price breakdown by merchant: http://uk.pcpartpicker.com/p/K9sRt6/by_merchant/
CPU: AMD Athlon X4 860K 3.7GHz Quad-Core Processor (£52.00 @ Aria PC)
Motherboard: Gigabyte GA-F2A88XM-DS2 Micro ATX FM2+ Motherboard (£39.46 @ Scan.co.uk)
Memory: Crucial Ballistix Sport 8GB (2 x 4GB) DDR3-1600 Memory (£38.33 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£32.40 @ Aria PC)
Video Card: EVGA GeForce GTX 750 Ti 2GB Superclocked Video Card (£90.00 @ Ebuyer)
Case: Cooler Master N200 MicroATX Mid Tower Case (£28.17 @ Amazon UK)
Power Supply: Antec EarthWatts Green 380W 80+ Bronze Certified ATX Power Supply (£31.83 @ Amazon UK)
Total: £312.19
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-08-05 16:48 BST+0100
here you go, It is impossible to include an OS in this range.
Keep in mind that you have to pay for playstation plus and games are usually more expensive on a ps4 so really this is less expensive than a PS4, That is actually how sony gets a lot of there money.
You can get an OS off of g2a.com and they work.
i would also recommend overclocking the crap out of that GPU.