Apple Music has duplicated ALL Music content

I've been looking into this for a while now and had a Eureka moment. First I'll explain what's happened.

Music (MacOS Sonoma) has duplicated my entire library. Prior to joining Apple Music (maybe a year back) I had some 12,000 tracks. Now every single track has both the physical entry, and a cloud entry. More than this, every single one of my playlists has been duplicated. (This seems to be continuing, some playlists are have up to 4 copies!!)

I attempted deleting the duplicate (empty) playlists but this then resulted in my actual playlists getting destroyed when I signed out and back in to Music (following another post that suggested this as a way of fixing the duplicated track problem).

I think I have the playlist issue under control as I reverted a Time Machine backup while offline and exported all the playlists to XML so I should be able to get them back, but the library... well that's all still duplicates.

What I have noticed is that each of the duplicates has a timestamp an hour out from the timestamp for the cloud version. Probably due to some incorrect DST conversion somewhere. And I was wondering if anyone had seen this? I'm thinking that being in the UK, the DST change not being synchronised with the US may have a bearing, but that's just grasping at straws.

Here's an example of what I'm seeing - note the date modified. This file has not been modified, nor has it been removed and the actual file time on the (external) drive is 01/04/2018 20:37, so the Cloud time is incorrect

Perhaps it's going to be a case of creating a new library somehow and adding absolutely everything back into it. I would love to hear suggestions, as anything I'm doing just fills me with the fear it is going to wipe the physical copies or increase the number of duplicates!