A quick update today. After a short break for holidays etc I was back on the car today turning my attention to the rear.
The offside rear turret is largely OK but had two holes one of them here:
I thought about patching it from the inside but access is pretty poor so I decided to do it properly from the other side. Sadly the turret strengthening plate is in the way
After removing a lot of spot welds this horror was found behind it
The bottom part of which forms the outside wall of the rear chassis leg. Not what you want to see. Thankfully it was localised only to behind the strengthening plate and the chassis leg itself is fine.
I conclude that the strengthening plate wasn't seam sealed which allowed moisture to get between it and the metal underneath where it sat eating it away. New metal incoming - but not today.