Managed to get the rows to display. Note exactly how. I was checking the javascript console for errors and although I had looked before I found an error for a rest call. (I have lost the url now) and when I ran it manually I got back
{"service":"","errors":[{"message":"RESTEASY003650: No resource method found for GET, return 405 with Allow header"}]}
Weirdly I hadn't seen this error before and haven't seen it since. After this the rows are now displaying. Maybe there is a cacheing issue from the older installation?
I still can't update report definition though. I am still getting the error above in the designer.