DS3 cab - front roof corner leak - and how to remove front panel above windscreen?

[Dunce]

Hi - I have leak that's coming in at the top corner of the windscreen and tracking down the corner post/pillar and into the footwell. Carpets are now out and drying out but I need to tackle the leak.

I can find posts showing that other people have experienced this, but little or no information on what typically casues the leak. Could anyone please shed some light as to what the problem tends to be - screen seal? weld seam? - and how it's generally repaired?

Also, any information on how to remove the panel at the front of the roof (between soft top and windsreen) would be really useful, since this is most likely going to need to be removed to access the area in question.

Thanks for any help in advance..