Thanks for the advice. This is the plan so far:
PCPartPicker Part List
Type
Item
Price
CPU
AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor
£118.37 @ More Computers
Motherboard
Gigabyte - B450 AORUS M Micro ATX AM4 Motherboard
£69.99 @ CCL Computers
Memory
Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-3200 Memory
£76.37 @ CCL Computers
Video Card
Sapphire - Radeon RX 580 8 GB NITRO+ Video Card
£172.48 @ Ebuyer
Case
Cooler Master - MasterBox Q300L MicroATX Mini Tower Case
£42.94 @ Box Limited
Prices include shipping, taxes, rebates, and discounts
Total
£480.15
Generated by PCPartPicker 2019-07-12 15:16 BST+0100
I already have a PSU ( Corsair CS650M 80+ Gold) & storage from old PC. I'm not fully decided on the GPU yet, but I only play at 1080p and the RX 580 seems to offer pretty good performance for the price.