Thanks for the first bit of constructive help. Interestingly in the appdata/local there was "Frontier_Developments", "Frontier Developments" and "Frontier-Developments"
I deleted all three, deleted the program files folder rebooted and did a clean install.
Now I don't have as many errors (they're still popping up though - about the A: drive bay door) but my download speed is now stuck at 0Mb/s. At least before it was downloading something, now it's downloading nothing. I've opened a support ticket.
Ugh.
All the pleasure of having been on the beta program was just undone by a broken release installer

It es me off because I would expect this from someone like Electronic Arts, but having gone all the way through from the first kickstarter, through all the betas to the release without a single real problem, to get to today and find I can't even install the release is kick in balls.