After doing a search and finding no results, I had to resort in posting a thread up.
Whilst in the middle of terrential rain/thunder/lightning storms yesterday evening, i noticed the headlining being damp where the rear interior lights are.
I proceeded to remove the plastic trim that holds it up and revealed a leak somewhere. The leak appears to be centrally sourced and then running both left and right down the trim due to its shape, ending up with the headlining being damp.
At first, i thought the seal around the ariel had gone, letting water in but under the ariel inside was dry? I have had a look at the boot seal and could see no splits, but the leak appears to be further back from there and higher.
I put my fingers in the two hinge holes/partitions and they appeared dry also. So i am now at a loss as to where the water is getting in.