I have spent a lot of time on this and made some progress. Firstly, for those who don't know (including my garage) the aircon drain tube exits into the transmission tunnel inside the drivers footwell, underneath the footrest ( same as Octavia (Screenshot_2019-05-22-21-35-34.jpg.9c10c83445932916cf97ab10ce1b31a2.jpg (1440×2560) Even though I had checked that water was draining from the scuttle under the windscreen, I took it all apart and found quite a bit! There was a build-up of debris (dense, like wet soil!) in front of the drain on the O/S, acting like a small dam. Just above there is a hole through the bulkhead, which should be sealed with a grommet - mine was missing. When I poured water onto the windscreen, which ran into the scuttle, it pooled in front of the 'dam' and whilst a lot went down the drain, quite a bit went through the hole into the drivers footwell just behind the accelerator pedal. I plugged the hole with a large amount of Bluetack, cover the whole area with Gaffer tapeand formed a really good seal - result no more leaking into car. I then removedthe mudflaps and prised the inner wheelarch covers away, to find a mass of 'compost' and dry leaves, mostly on O/S. Why this isn't part of the service schedule, say every 50k miles, I don't know. It would take a mechanic 10-15 minutes to do this and prevent a lot of problems. Having done all this andchecked the drain tube (shown in photo) was clear, I ran the car with aircon engaged and the drain tube end put in a bowl - water dripped in, so all seemed to be working, so reseated the tube end into the chassis hole and it then dripped out underneath the car. For the moment, I'm hoping it's all sorted. Placing towels etc. underneath the felt-type soundproofing under the carpets, to try to dry everything out. I'm now going for a beer and a lie down!!