I guess this is a typical question for all you dubbers out there

I have a 5 door mk 2, I cant seem to find the source of the water leak that is turning my rear passenger floor (behind drivers seat) into a reservoir.
Its not just a little bit of water..which is starting to annoy me as items that were on the floor are now waterlogged lol
The window seal is damaged, it seems about 50mm too short, the previous owner had stuck general purpose silicone in the gap as a temporary measure...and then i came along and replaced the silicone with proper window sealant..now i agree that siliconing up the seal is a "amature" way to do things...but its Xmas and I'm on apprentice wage lol <-- good excuse ey

I will be replacing all seals soon though, even with the extortionate price they cost...
The problem is still there, I have made this weekend into a "sort out the golf weekend", so if anyone could advise me of where they think the leak could be sourced, and how i can rectify the problem, i would be much obliged.
Thank you

Ga.