HI
finally found time time to rebuild the photo library from scratch.
it took 2 Hdd or sd cards formatted to osx journaled and large enough to hold the library a few times over ( e.g 2 discs with over 128 Gib space on each )
I copied the iPhoto library to one backup disk and locked it away safely just in case!
I did not have enough space on the Mac to build a new copy upon it so i moved the iPhoto library lock stock and barrel to a second external Hdd
I then opened it in iphoto and selected all the events and exported them to the same external Hdd using the export function, selecting the current version of the file, in the original format and the event name as the folder
it did not export 41 movies ( mov files ) and i have no idea why they are no longer compatible, but it listed them by name
i then created a new iPhoto library on the Mac and imported all the events I exported
it messed up a few dates etc but I can correct those in iPhoto with the menu options
Plugged in both the iPad mini and iPhone and it has synced with no issues
I've lost the faces etc so I'm going to redo those over the next 12 months
20k images in 500+ events and shrunk the library from 75Gib down to 45 Gib as i no longer have both original and modified images.