vw polo 9n water leak

Hello, a year ago i bought a vw polo 9n mk4 or mk6, whatever you want to call it. I've got a problem with the back end concerning rain, when it does rain the boot is soaking and the chairs damp, I've taken them out and stripped the back end to dry out which now resides in my garage, i cant find an exact point of water entry but i have found what looks like water wells on both sides of the inside of the cars boot. i took that little plastic trim off the roof of the boot and very gently slightly pulled the roof down and found lots of water droplets, big ones, I've sealed up the antenna on the roof and it has made no difference. there also appears to be a metal parting in the actual roof of it on the inside but nothing on the exterior. Has anyone else had this problem? please help as i dont really want to spend a lot by taking it to vw if i can do it myself. Thanks very much.