Thanks for all your ideas but I can comment as follows
- the windscreen is the original factory fitted and so rules out any potential issue caused with the fitting of a new windscreen
- I checked the aerial and also from the inside by removing the centre console in the roof panel and completely dry
- I've since poured water just into the roof rails to see if was getting in through one of the fixing points and no water came in
- I also poured water just into the gutters where the rubber strip is located and no water came in
- I then poured water across the top of the windscreen where I'd applied the sealing tape and no water came in
But then if it's out in the rain for 10 minutes then water is starting to come in !!!
I know what you are saying that you'd expect the screen to crack first. However, with the way the Espace is constructed with a galvanised body shell to which is bonded the GRP panels, it may depend upon whether the screen is bonded to the galvanised body structure or the the GRP roof panel and having not had a screen out I don't know how it's fixed.
Whenever I'm on a rough or pot-holed road, and that now seems to be the majority in the UK, there is often a creaking noise from within the front roof area. So, whether the GRP roof panel has come adrift from the steel body shell or the screen bonding become detached from whatever it is fixed to (the GRP roof panel or to the galvanised steel shell) I am not sure and won't be until I have time to get the screen out. But in the meantime it just has me baffled how water can still be getting in