Check the gaskets on the wiper bezels they perish & are a poor fit. They are from an MGB. I use black silicone to seal them on renewal. Grease the drive pinion where it comes through the bezel & fit an O ring in the groove.
It could be water from the heater box drain. You will find a spigot end on the housing low down near the bulkhead. It might be water coming in through the drain, older cars had pipes taking the water away. A cover over the heater inlet when parked might help but also check the drain holes on the box above the bulkhead are not blocked.
The two screws that hold the bonnet hinge on can be removed & clear silicone put in the holes before screwing up again.
