Water leaking in 2 places:
1) Rear wiper shaft rubber bush/seal at window penetration: Rubber flange part broken away from tube part of sealing bush and consequently leaking. New bush fitted, with added rubber gasket lubricant to ensure seal and shaft lube..
2) Joint/seam between roof panel and side panel (exterior steel body panels), in the recess for roof rack attachment, below the concealing trim. Removed the trim to reveal a 90* angle sealant fillet, sealing the joint between the 2 body panels at the outboard edge of the bottom of the recess. This seal had a hairline crack, running from rear of car 2/3 way to front of car. Hose test showed this leaked. De-greased and jet washed the crack. Left to dry and then progressively built up a crack filling seal using "Captain Tulley's Creeping Crack Cure", a capillary seal that sucks into the crack. Takes several applications to fill the crack.. The crack can be seen highlighted by the white sealant in the attached photo.
This crack may explain damp ceiling and rear quarter interior linings as well.

 

ps, the covering trim ends were blocked with debris under the trim, holding ponding water over the crack, increasing water penetration. The minute crack can be seen in the 2nd photo, highlighted after one application of sealant which had partly sealed the crack. I assume the front windscreen braces the front end of this joint, whereas the tailgate hole allows more flex and consequent sealant cracking at the rear.