UKPassats

So, after 8 weeks of sunshine, we've had our first dose of continuous rain. This morning I opened the boot to find a load of water had gathered inside the tail gate! It came pouring out from inside the interior trim. I removed the panels where you'd stick your hand in to change the bulbs, and even more came flooding out. Where did this come from? Never have I had any trouble like this in the last 4 years of ownership.

Recently I did change the boot lock as it failed. If I didn't align the lock well enough, i.e. if the door closes and locks, but has a gap, could this cause it?