On the trail of the mystery rainwater leak into the drivers footwell I happened to flash my UV torch across the carpet and it lit up like a Christmas tree on the left hand side, right where the heater O rings would leak if I had any.
On closer examination the coolant is coming out from the heater housing, not the hose connections, so the 6 month old Nissens matrix has failed!
Naturally, when I fitted it, I did it with dash out, and didn't cut any of the metalwork in the way, so, unless I go into butcher mode, the bloody dash will have to come out again.
This car really is possessed by demons and is so high maintenance compared to the old blue one that just keeps on working. There is going to come a time where I just run out of patience with it- and that time's coming very soon.