You can roll back your version of iOS. I haven't done it for a couple of years but it's not too hard. It's basically having to do a version of disaster recovery yourself. There are loads of online tutorials for it.
The only other suggestion would be to set your device as a hard drive in Mac OS or Windows and have a browse through the file structure to see if the raw data is in there somewhere.
Thanks for the replies. I didn't take the risk to roll back versions because I read about the risks. I tried to sync the app with the Cloud (iTunes doesn't work with apps anymore on ios11), and this didn't work because MyPhoto wasn't on the list.
Anyway I thought that was it, and as a last resort I just googled 'copy app from iPhone to iPhone'... and found a program called 'Anytrans'... So I downloaded and it found everything in the app and I was able to download everything in one go to my windows laptop.
Just been having a look at this program... Its quite impressive... It can transfer anything from one device to another...app, pics, anything... Very very handy. So well recommended.
Anyway, crisis over. Thank you for your replies.