Hi wp, thanks for your help,
I 'think' I did everything the correct way in terms of renaming units and forms, but can't now be sure.
When hdpi became available, I moved the project to an hdpi PC and worked on it there. The problems appeared when I moved it back to another folder next to the original. I found that it pointed to the old 'published' and 'languages' folders These had never been used on the second pc. I have now edited the lpi file manually to correct it. Things seem to work properly. Everything is now named correctly and everything seems to work, except that I cannot force po file updates from the Project|Options. I think that is a separate problem and will open a separate thread, after some research and experimenting.