Simon did you ever get your rear door seal/leak sorted ??
I have had this intermittently since new, and have been pouring (no pun intended) with the service manager today. Having given this far more attention than before, I have found a probable culprit.
Look at the back roof as it drops down towards the rear doors. There are two body lines ( a small recess) that goes down onto and under the back door top seal on the body. One lines up where the two doors meet, the other one is above the big door and matches up directly where I get drips of water on the inside trim.
A flat seal with a 3-4mm wide gap under it doesn’t look good for sealing.
At the same time of looking I also noticed the (big) back door seal is coming adrift near the bottom as it curves with the door shape. Having read about other stuck bits of trim coming loose and/or falling off, I have a deep suspicion that the double sided tape my not be as good a quality as we would like and is starting to give up the ghost as time goes on OR the surfaces were not clean enough/contaminated when applied !!
Ineos are now saying that ny door seals with a loose surface of 120mm is a new seal and anything less is a stick back with LOCTITE 466 glue. Although I have no idea what 466 glue is tbh.