Might have to hang my head in shame a bit on this one.
I oiled up the hub. And it made no changes. Because I did it quickly, I thought I might not have put enough in.
So did it again making sure plenty went in.
Still squeeked.
So I had a proper look at the hole back end and noticed the cone on the non-drive side had worked loose. Combined with the fact that the stays for the rear mudguard had been compressed it meant that when the bike was leant over to the left the trye was rubbing on the stay.
Also noticed however, that a plastic bag had somehow wrapped itself completely around the cahin pusher and the two rear cogs. It was so ingrained into the mechanism that only the very tips of the smaller cog were showing, which meant shifting had been a bit weird, and it was wrapped around the spindle of the moving jockey wheel and meant that pedalling seemd like a lot of effort of late.
Now all that's gone the bike feels good again.