PCPartPicker part list:
https://uk.pcpartpicker.com/list/g38s2R
Price breakdown by merchant: https://uk.pcpartpicker.com/list/g38s2R/by_merchant/
CPU: AMD - Ryzen 5 1600 3.2GHz 6-Core Processor (£187.14 @ Aria PC)
Motherboard: MSI - B350 TOMAHAWK ATX AM4 Motherboard (£96.46 @ Box Limited)
Memory: Corsair - Vengeance LPX 8GB (1 x 8GB) DDR4-2666 Memory (£72.96 @ Aria PC)
Storage: Western Digital - Blue 250GB 2.5" Solid State Drive (£79.68 @ Aria PC)
Storage: Seagate - Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (Purchased For £0.00)
Video Card: Asus - GeForce GTX 1060 6GB 6GB Dual Video Card (£267.43 @ Amazon UK)
Case: Thermaltake - Versa H24 ATX Mid Tower Case (Purchased For £0.00)
Power Supply: XFX - XT 500W 80+ Bronze Certified ATX Power Supply (Purchased For £0.00)
Total: £703.67
It will do well in gaming giving you well over 60fps @1080p. I couldn't tell for sure if you have the G4560 or are thinking of getting it and then upgrading to i5 7400 in the future. Please do clarify that. With the above mentioned build, you get twice the cores than the i5 7400 and those come in handy when editing videos and playing games that support multi-cores; while still getting great performance in single threaded usage.