Was on my way home from mot station, 300m from my house then steam pouring from top dash vent and majority of coolant dropped on the road approaching my house.

If heater matrix had gone wouldn't leak just be inside the car?

 

have just been through all that, mine was just steaming up the interior all the time, then i found water on the passenger footwell,,its a bloody nightmare to do(DIY) BUT CAN BE DONE,
take it to dealer and=£200+ for matrix / plus 5/6 hours labour.......... .


check the pipes from your engine to heater,as they might have bust,