Reseating seems to have worked for mine mate, I think it was just because the car was parked on a slope during that heavy rain rather than there bring actually anyyhing wrong with the seal.
Matt, just had another look at the photo of your house and I think you need to be parking 'nose in' to avoid the risk of your boot flooding. Parking 'nose down' can lead to the water overflowing from the channels on each side of the tailgate instead of running away behind the rear lamp clusters.
Hi, do you still have any door seals?
thanks,
Wil