Firstly thank you for your help this evening - as always top support.
My current plan is that I have requested restoration of the 2 sites from backup after which I'll setup a duplicate test site on the same VPS. That way I can apply the updater and test it properly so we can find out what's happening.
No problem Vince - I got the sites restored OK and have a test site which I plan to take a look at in the next couple of days. I also hope to work out what's going on with error logs on the server.