[Horokiwi_Hori]

Hi men and women of the forum.
I literally woke up to a nightmare. After a short drive yesterday, my 2013 E92 M3 (ex UK) warned of low coolant when I got home.
This morning when I checked there is a puddle under the car in line with the rear set of O2 sensors behind the cats.
I removed covers and took the attached photo.
I have coolant dripping once ever 8 seconds from what RealOEM.Com labels "Water outlet hose, splash wall, right" on a slide called "> Heater and Air Conditioning > Collective function group" - M3 diverse small parts.
The pic I took shows a drip forming on the part that looks like a breather. The photo is taken looking up the right-hand side of the DCT, with the pan just obscured and the rear O2 sensor wiring visible.
What I need help with is where to from here to resolve this leak?
The RealOEM diagrams don't clearly show what the "Water Outlet Hose" drains.
I assume it is the heater core area in the cabin? The leak roughly lines up with the door hinges - I imagine its in the vicinity of the heater core.
Do I have to embrace a heater core replacement job?
I'm stuck friends. Any help will be greatly appreciated.
I guess I may as well drain the system while I try and get a real understanding of the problem.
Thanks for all the history, I have searched and founds plenty of distractions. no Snap moment.
George in NZ