Not sure if the link I embedded will work for you so here is a breakdown of the parts:
CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor £144
Mobo: Asus Z97-A ATX LGA1150 Motherboard £116
RAM: G.Skill RipjawsX 8GB (2 x 4GB) DDR3-1866 £ 55
HDD: Samsung 840 EVO 120GB SSD £ 54
HDD: Seagate Barracuda 3TB 3.5" 7200RPM £ 77
GPU: XFX Radeon R9 280 3GB Double Dissipation £150
CASE: Corsair 200R ATX Mid Tower Case £ 50
PSU: EVGA SuperNOVA NEX 650W 80+ Gold Mod ATX £ 63
DVD: Samsung SH-224DB/BEBE DVD/CD Writer £ 11
OS: Microsoft Windows 8.1 (OEM) (64-bit) £ 74
Keyboard: Logitech K120 Wired Standard Keyboard £ 15
Mouse: Logitech G402 Wired Optical Mouse £ 35
TOTAL £844
A generic mouse and keyboard from any website you are buying parts from would save about £35-40, dropping the HDD to 2TB would save £15-20, dropping to a Pentium G3258 would save you £100, overall saving you £160 bringing you closer to your £600 budget but if you spent an extra £65 on the GPU to bring it up to the R9 290 you would see a massive improvement in FPS and give you an extra year of comfortable gaming before needing to upgrade the GPU IMO.