Well the mobo arrived today which is a great turnaround time. Re-install was reasonably easy (they ought to make motherboard designers remove mobos from cases, that part was a PITA) and, as I type this, everything seems to be running OK
One interesting development was that I had to send the board and CPU back together as it was a pre-installed bundle. The board I sent back had a Ryzen 5 2600x 6 core processor...the one it came back with is a Ryzen 7 3700x 8 core processor. Hopefully that's a win 😊 but, if not, at least it works!
Thanks again guys for all your help