I took the plunge and removed the bumper, rear lights and parking sensors and found the problem!

Boy did I find the problem!

Loose air ducts into boot letting in water into rear quarter panel corners. There was a few pints on each side! This was being soaked up by sound proofing foam.

I removed four ducts, jammed them up with sealant and put it all back together once dried.

Fingers crossed. I can’t believe I actually did it with no problems! Check out these pics! My GF is well impressed!

Feeling pretty pleased with myself too as I’m usually crap at this kind of thing.

Thanks guys😎👍🏻