Seems to be coming from the heater assembly, but the water is crystal clear and there's no loss of coolant. I'm thinking blocked air con condensate drain line.

Before I get under the car to see if the drain line is clear, has anyone else had this issue...and the solution?

80 views and no responses - must be a rare problem eh? Tracked the source of the water down to the radiator in the heater box (accessible through the opening for the pollen filter). The rad was dripping wet (normal I'm told - it's A/C condensate).

For some reason this water wasn't draining away, but running off into the footwells. Pushed a flexible drain rod from above and below through the drain hose. Nothing obvious blocking it. But condensate is now flowing out from below the car as normal, so hopefully problem solved.