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It could have a butyl seal in it. I have read somewhere that they’ve sometimes perished on other cars.

TBH I’ve search that many forums and even different car types Iim not 100% sure what I’ve read.

Well hopefully some dry weather this weekend and I might give it a go (sealing the wing channel) are you planning on using a setting or non setting sealant?

Fingers crossed

Sorry forgot to add … you’re probably right don’t think my car has had any damage on that side so most likely to be a similar issue..

I’ll let you know how I get on

If the car is not a daily runner, you could take the wing off and inspect, then apply some sealant between the top join.?
Similar to what you considered a bodyshop to do, but DIY accompanied with beers, and in slow time.

I plan to remove my drivers rear wing in the coming weeks, it sounds like a good idea to run some silicone along that top join to hold off any future issues.

Car isn't a daily driver so removing the wing is definitely an option....and becoming more and more likely.
My brother in law is a mechanic so I might call on him to give me a hand and get the wing off.
Not really sure what I'm looking for but cleaning up all the joints, and checking for any obvious perished sealants would be a worthwhile exercise.

Ive mentioned this product a few times " Captain Tolleys"
I used it to cure my leaking rear lights and also my daughters Citroen which had a huge water leak

On amazon

https://www.amazon.co.uk/Captain-Tolley ... 549&sr=8-2

I’ve ordered some captain tolly’s off eBay should be here Saturday … if it’s stopped raining I’ll dry everything out and give it a go. I wail probably “belt and braces” seal the guttering too. Then do lights and vents (which are dry) as a precaution for future leaks.

Just ordered some Captain Tolley. So today, I'll get the drainage channel cleaned out and remove sealant that I've previously applied.

I'm almost at the point where I doubt anything will work but I'll give it a try and see how it goes. Fingers crossed.

Bit of s breakthrough j think.
Usual drips in the boot this morning but got the hose out and aimed it into the drainage channel...but specifically thr bottom.
No water coming in.
Aimed at the top...water comes in.
A bit of investigating and I noticed there's a gap at the top of the channel....right under the quarter light window both sides are the same.
So that's where the water is entering and working it's way down to behind light and dripping in.
So I guess now I simply seal that gap...but I'm also wondering if it's a designed drainage channel.
Any one have any knowledge of that gap and its purpose??

May be some success here too

Put Captain Tolly’s down the gap in the drainage channel and encouraged it down the seam with hair dryer then about 2 hours later put a maul bead of silicon sealant along the complete length and smoothed out.

It’s been raining where I am again this morning and everything is still dry. Take it out later see if it remains so.

I still haven’t done anything to the boot vents or tail lights as yet.

I’m not sure what the gap is you are referring to is for but mine now has silicone in it.

Z4phil, The gap appears to be a channel of some sort right at the top of the wing. Just below the quarter light window. It's the same on both sides.
Driver's side appears to drain fine - hosing that area doesn't result any water entering the boot. But the passenger side was a different story. Hosing that area resulted in immediate drips just above the rear lights. So the channel is either blocked or damaged inside the wing. No way of fixing it without removing the wing. And even then, I guess it's not a sure thing that I could repair it.
Here's the silicone in place and and another inside the boot after rainfall. Typically, that would be wet with water having leaked in.

I checked again this morning and there's about 2-3 drips so I've maybe missed a tiny section. I'll apply some more silicone when it's dry.

So far so good with my Z but I’ve not put the hose pipe on it yet. I’m away now for a week so it’s back undercover and I’ll give it a go on my return

Ill also have a go on the near side to see if it drains away too

It looks like the silicon on the wing has resolved the issue lots of rain here in the last week an no issues. Proper fix would be wing off and and new butyl seal. But I’ve got other priorities on the car to resolve so I’m going to leave as is go now and inspect every month.