Just had a leak from above c-pillar on my golf, leaking onto parcel shelf. I removed trim that goes from c-pillar to c-pillar( very carefully) and was lucky to be able to reach fitting on top left as you look in the boot ( as rhyso said ). Scraped my hands a couple of times but was able to reconnect the fitting and put some insulation tape around it. Don't pull any of the cables or the pipework until you have found both ends of the conector though.