OK ... I haven't had to do this in a while, but I basically followed the troubleshooting steps in the SysAdmin Guide.
Not sure which did the trick but I rebuilt the triggers, then deleted the templates_c contents (which I do on upgrades anyway) but also deleted the Config.IDS.ini file, which I didn't do.
Anyway ... now the form appears and processes fine.
OK it seems that it is some issue with transferring to my test system ( I myslqdump and mysql ) and it seems there are constraints that are not allowed. I did manage to get the transfer right once I completely trashed the dev database. I'm assuming that the sequence of loading means it is checking against 'old' data.