Info needed!

I'm reasonably new to Land Rovers but am a keen amateur mechanic. I recently bought a Discovery2 TD5 which needed a new head gasket as it was pressurising its cooling system and over heating gently! I also changed the water pump whilst I was as it.

Anyway, 2000 miles later without using any coolant or oil to speak of it's been 'gurgling' from behind the dash/radio area. Now it has started not producing heat from the heater when idling ( waiting in the queue at Maccy D's drive through) but then heat is produced shortly after driving away. But today it stopped heating, didn't produce heat after driving away and then the temp gauge rose just above horizontal and spat some coolant out onto my drive as I got home through the over flow pipe on the header tank(approx 3 miles from when the heater stopped).

Any one had similar issues?

Air lock, needs good bleeding of coolant, probably caused by cracked head