I just emailed penfold about some of these, several had me really interested, at least until I read his saddening reply to my questions about them:
I had a go a few the other day and the drive just makes a scratching noise, in the end i had to clean my drive to get it to read disks again. :-(
I was gutted myself which is why i kept trying them and damaged my drive trying to find some that worked. They were all stored in a shipping container for 15 years. So open to the elements, hot & cold + damp. I've just had a look under the metal disk cover and sure enough under a light you can see surface damage. I very much doubt they can be saved.
My uncle kept all his old Amiga bits n peices from when he had a computer shop. I seem to remember he also had many demo's like this. I see him next week so will ask and find out if i can get hold of them just to make some copies. If copies is all you need, ie preservation then i'm happy to get them to you free of charge.
Hopefully we will have some of them in ADF format in the near future then