Thought I'd add my experience to the leaking boot problem classics often have.

V296 WRX wagon had a pond in the bottom of the boot for a while and with the dry weather decided it was time to tackle it.

So here's the method I found. If you want to trace a leak, and can see where the waters getting in the boot (for me after removing the interior I could see it was dripping from the a panel section near the offside tail light) dry the area and starting low work upwards, moving very slowly wash over the car with a hose pipe on a small steady flow watching the point where you can saw water appearing inside - as soon as you see water re-appear your in the vicinity of the leak. Dry the inside and repeat until you narrow it down, bear in mind that it can take a while for all of the water to work down from the leak so give it time for the leak to stop in between goes if you want to be sure you've found it.

By using this method I traced the leak to a tiny hole in the panel seam at the end of the gutter on the flaming roof - the water was running down the inside of the pillar and dripping down around the lights, I raked it out, splodge of Chemical Metal and leak gone! Looking forward to not having steamed up windows in the cold weather now

 

That now makes SIX areas to check for leaks in the boot.