My 200tdi has had a coolant leak for a bit now to the point where it needs a topping up every day!!

I'm pretty sure it's one of the heater hoses at the back of the engine near the bulkhead. When I was trying to find the leak earlier, I ran the engine for a bit to warm the coolant up, then when I switched off, I saw a lot of steam and water spray out in the nearside of the engine bay.
Reckon this is a heater hose going? I've ruled out the head gasket. This happened to anyone here?

Cheers!

Is there a core plug near there? If so it could be that