I noticed a thread in the Y10 forum about "extreme condensation" and it had a happy ending so I thought I'd test your imagination / experiences with my problem.
I have a series 2 Thema (LHD) with Air Con and NO sunroof.
It has a significant water leak into the front passenger footwell.
I have pulled back carpets, but can't lift the plastic backed sound deadening that is moulded to the shape of the bulkhead and which fits up behind the dash. Pulling back the carpets did reveal that the water was getting in quite high up on the bulkhead and was not getting in at the door seals.
I had the windscreen removed by RAC Windscreens to have it resealed (and they broke it...

). Fortunately able to get one from the Thema Consortium for £40. Much better than the £220 quoted by RAC for a SAAB 9000 screen.
The removal / refitting of the screen made no difference to the leak.
I've had all the surrounding windscreen trim removed and can't track a point of water intake. I've alse removed all the plastic trim from the scuttle and cleared away debris, but there is no sign of a water pool collecting in this area.
I can only imagine that water is somehow accummulating in the aircon unit and then seeping into the felt of the sound deadening at the bulkhead opening where the aircon evaporator unit bolts to the bulkhead. In my LHD case, this is directly behind the glovebox, but it would be behind the instrument panel of a RHD car.
Does anyone have experience of such a fault or any other ideas?