MG ZR Heater Matrix Problems

hot air as stopped coming into the car just reacently ive had a new thermostat and the system as been flushed as well has the heater matrix box there is no problem with the head gaskit as the car runs at its normal tempreture and shows no s...

heater stopped working and oily substance in header tank and water in header tank pressuring up. the pipes into heater matrix one is hot the other is cold after bleeding heater went hot for a few minutes then went cold again