It does strike me that if it's never going to be read and is simply taking up space, the best back up would be to put all the paper in the cheapest lock up storage facility: Can't speak for your side of the pond, but if you do an annual rate without immediate access here, it's pretty cheap.
Sssh: That would do you out of a nice little earner!
My mother died last year, leaving a very active sole medical practice behind. Seven year record retention required and no one wanted to take her patients/practice on.
Her former office manager/secretary/bookkeeper/best friend got a very nice new metal shed on her farm, and a nice set of filing cabinets (under some well secured tarps against leaks).
On the first damp day after the seven years are up, we'll have a big bonfire. We expect not a single request from those files, but we gotta keep 'em at the ready. Of course, my mother took her notes cryptically, so no one else could even use them if they get them.
-jk