iCloud Drive wiped clean after iOS 10 install

I installed iOS 10 onto my iPhone 6 Plus at around 8pm last night (German time).

This morning I noticed that my iCloud Drive was empty.

I'm now following the instructions here to recover the deleted files (all with timestamps showing deleted at the same time as the iOS 10 install was taking place).

Worth noting that the Restore Files interface is not very helpful. I have over 900 files to recover and if I select them all and press "Restore", it thinks for a few minutes before saying the operation failed try again later.

If I try to recover a single file, it sometimes tells me that operation failed "try again later", then if I try exactly the same thing again it suddenly works! Could be a long day...

Can't believe I pay for this service!

Update: Having now finished recovering files, I notice there are still a lot missing. Also the iCloud app on iPhone isn't recognising the files I've managed to recover. This is very frustrating...