Decided to look at the tailgate lock as it wasn't latching all the time. I took the door card off to reveal a pretty much intact vapour barrier. The area by the lock was torn so someone had been there before.
I operated the door release button a few times to get a better idea of what the problem was.
I could hear the switch click and the lock motor run, however sometimes the motor didn't sound like it was running back to it's rest position. I decided to take the lock mechanism out for a better look. Getting these out of the door is a bit of a game due to the confined space it's in. Once out I tested it, it seemed ok but I noticed that the grease had begun to harden. I gave it a good soaking with WD40 as it's solvent works wonders on hard grease. Not really finding much wrong with the lock, I took the handle off.
The first thing I noticed was one of the 3 bolts had broken out of the handle. The next thing I found was one of the release lever return springs has broken, the broken section was jamming the lever. I had a dig through my springs box and found one that would work after a bit of a trim. I then drilled a couple of holes in the broken plastic bolt fixing so I could hold it with a couple of screws.
On fitting the repaired handle I discovered that the large rubber seal had swelled with age stopping it from fitting correctly. I cut a section out the middle to allow it to fit again.
Once done I resembled the door, I closed and opened the door more times than I cared to remember, it now works as it should.