mk 1 Focus boot leak

[Loofer]

I've had a boot leak for years now and I'm determined to get it sorted but I'm running out of ideas on how to do so. The red dots are where the water is appearing, in all but one (3rd from the left) it isn't visibly running down from anywhere as you can see from the close up, it just pools. It's obviously coming down a seam in the bodywork but I can't find a source.

 

I've siliconed every hole in the tail light fittings I can find and the two rubber grommets at the top edge of the boot opening, removed and re-sealed the boot seal rubber and sealed the boot air vents behind the rear bumper all to no effect.  I've had the bumper off but there's nothing external in those areas to show a leak.

Anyone have any ideas? the only thing I can think of is maybe there's something going on under the roof trim but I can't see a way to get that off easily to check.

 

[DaveT70]

Tailgate seal, if it's definitely not the tail lights

Then rear backlight (glass) to body seal has broken down

Then rear 1/4 lights, same as above

[Loofer]

Checked the glass but it seems OK, definitely seems to be coming down from within the bodywork at the rear as opposed to the tailgate though.