Ok,
Firstly get the spare wheel out, get under neath and pop the grommit in the middle of the spare wheel well to empty it. Then have a squint in the pass side pocket where the jack sits, it was full in mine too. Again theres a plastic grommit you can pop to empty it.
Then take out the rear lights and silicone up the seals.
Then look at the cabling running in at the top of the boot. I had to silicone those up aswell.
I currently now have reduced a torrent to a tiny trickle so have something else to find.
Hope that helps