Punch Technology mATX AMD Ryzen 5-3400G 8GB 240GB SSD No OS Desktop PC - £274.97 @ Laptops Direct
This is a fantastic price for a barebones gaming PC. The Vega 11 chipset can turn in a reasonable mid-range performance and you could add a dedicated card to boost this further to make it handle MS Flight Sim well.
Could definitely benefit from more RAM and bigger SSD but the core machine is very good for the money.
* Please note that all prices are correct at the time of posting. However prices can vary quickly and significantly without warning.