Best CPU for £100

Made the motherboard a H97 motherboard to work with the intel processor, dropped the CM 212 evo since it can't be overclocked, and made the RAM dual channel instead of single channel.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor (£138.52 @ More Computers)
Motherboard: MSI H97 PC MATE ATX LGA1150 Motherboard (£65.81 @ Amazon UK)
Memory: Kingston HyperX Fury Blue 8GB (2 x 4GB) DDR3-1866 Memory (£30.99 @ Amazon UK)
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive (£68.34 @ Aria PC)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£34.74 @ Aria PC)
Video Card: Asus GeForce GTX 750 Ti 2GB Video Card (£98.99 @ Aria PC)
Case: NZXT H440 (Blue/Black) ATX Mid Tower Case (£84.99 @ Amazon UK)
Power Supply: Corsair CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply (£56.99 @ Amazon UK)
Total: £579.37
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-02 18:02 BST+0100