Not too much over budget , Yes the GTX 970 is better than the 290 but by a very small margin and probably not worth the extra 55 Pounds , I'd spend those towards an SSD maybe .
Your build didn't include HDD too so I added one.
PCPartPicker part list:
http://uk.pcpartpicker.com/p/M4TByc
Price breakdown by merchant: http://uk.pcpartpicker.com/p/M4TByc/by_merchant/
CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor (£131.94 @ Aria PC)
Motherboard: Gigabyte GA-H97M-D3H Micro ATX LGA1150 Motherboard (£64.74 @ Aria PC)
Memory: Crucial Ballistix Sport XT 8GB (2 x 4GB) DDR3-1600 Memory (£57.99 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£35.94 @ Aria PC)
Video Card: XFX Radeon R9 290 4GB Double Dissipation Video Card (£223.19 @ Scan.co.uk)
Case: Cooler Master K280 ATX Mid Tower Case (£31.33 @ CCL Computers)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply (£43.76 @ Amazon UK)
Total: £588.89
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2014-10-06 15:02 BST+0100