@blackbird71 It looks like the file I have managed to recover is corrupted. I only found it by using the deep scan function of a file recovery program; the hard drive is basically trashed.
I have a live off site backup running, but I don't back up all of the AppData data folder, only a few important apps. Unfortunately I set the backup up a few years ago when Opera stored it's settings in AppData\Roaming\Opera, so that's what I have backed up. I didn't realise that Opera changed at some point to AppData\Roaming\Opera Software and that folder wasn't backed up.
Thanks for your help, much appreciated.