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it may well be the screen ,
but you may also want to check a place by the bonnet resting bolts on the windscreen scuttle, these have small rubber tops on the bolts a few inches from the windscreen wipers, the reason for this is the scuttle can rot out in this area,
also the aircon system may be leaking into the passenger footwell , its not aircon as such , but condensate from the cooling action
and finally , the heater matrix, make sure the coolant level isnt dropping for this one
hope you get it sorted
BB