Guys, just so you know, we managed to track down the leak on my tailgate, altough havnt yet found a solution. The problem despite being diagnosed as the high level brake light by the dealer, is actually caused by the fact that the inner and outer skins of the boot are not sealed around the edge. This results in water ingress no matter where on the boot the water is poured. Silicone or mastic around this edge might help the problem.