Thanks everyone for the help.
I have just moved on. Since, it was taking such a long time between replies I just went ahead on Friday and restored the old site and tried again. I ended up with the exact some issue. So, I restored again and have been developing the site on version 2.1.1. Not ideal I know, but deadlines are deadlines.
I saw the other replies over the weekend. @Michael Hessling the file is there (I saved a backup of the errored site), thanks for the suggestion.
And @Kurt Deutscher that might well have been it. I looked back and there was a module theme that was missing in the cp_theme folder. I will be on the lookout for it in the future.
I am a little gun shy now, more from the lag in getting support than anything else.
Again thanks for the help and the check up to see how things are going.