Comrade Jayray

2406 was released 2 days before the Ryzen 3000 launch, so its likely to work, but not 100%.. there is 1 newer BIOS released since. 

you will need to spend more on an X570 board which will cost a lot more if you don't want to touch the bios, or find a computer store that can update it for you. i doubt current stocks will have the new bios but you can check with the seller to be sure. MSI's B450 boards have BIOS update buttons that make it easier for you to update it.

PCPartPicker Part List
Motherboard: MSI - B450-A PRO ATX AM4 Motherboard  (£78.19 @ CCL Computers) 
Memory: Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-3000 Memory  (£63.95 @ CCL Computers) 
Storage: Crucial - P1 500 GB M.2-2280 Solid State Drive  (£54.56 @ Amazon UK) 
Storage: Seagate - Barracuda Computer 2 TB 3.5" 7200RPM Internal Hard Drive  (£49.98 @ Aria PC) 
Case: Fractal Design - Meshify C ATX Mid Tower Case  (£79.99 @ Amazon UK) 
Power Supply: Corsair - TXM Gold 650 W 80+ Gold Certified Semi-modular ATX Power Supply  (£67.99 @ AWD-IT) 
Custom: RTX 2060 super (£318.00)
Custom: Ryzen 3700X (£262.00)
Total: £974.66
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-07-05 01:51 BST+0100
Wait a few days for both parts, also you'll need to update the bios before using the B450 board.

Wait for July 7th. Zen 2 comes out then.
 
Also, since you are in England I assume, use uk.pcpartpicker.com to get UK pricing.

2700X's have been going for $200-250 and Vega 56 has been going for $280-300 for like a year now. I'd try to skip the slow 2TB drive, pick up a 1TB M.2 for about the same price(of both) and if you need more storage down the road you can always add drives.
 
Also brand new AMD cpus and gpus which are going to be significantly faster in every single way are coming out in just 2-3 days, please don't pay MSRP for previous gen parts.
 
At this price point, I'd recommend to fit a monitor upgrade to 1080p144 or 1440p144 in somewhere. Even with a 2600x and a slower gpu, I think you'd be much happier with getting more of your performance in games out into the physical space with a monitor which can actually display the frames you're getting than pretty much bottlenecking all of the parts you actually interact with.

yes, the TX650 or even a 550 is a good idea for your build.

I'm running a 650W PSU if that helps you decide.  

you should be fine with the 650w, just get a reliable power supply
can't help you much with choosing one, there's a PSU tier list thread somewhere