Had an inch of water in rear footwell this morning on the bug, this is the first time its sat in
the rain since I replaced all the seals. It was happening before but I thought the seals would do the
job. I've got a new set of carpets but I cannot put them in until I track down the leak. I'm
stumped as I'm pretty sure its not coming in via the doors, no trace of water in the front. Anyone
got any clever ideas or experience of the same?

if there's no sign of water penetration through the windows & doors then it's possibly getting into the heater channels and coming out through the vents in the footwell and under the rear seat... worth investigating