Fiesta Courier heater blowing cold air!

[Courier]

Help! Fiesta Courier van on 02 plate, heater blowing cold air. I have done the following;

1. Replaced thermostat.

2. Replaced heater matrix and flushed system. Re-filled 50/50 coolant. (How many litres should system take?)

3. Removed and bypassed HCV.

4. Thermostat bypass hose to header tank found to be blocked. Unblocked and warm water now flowing freely.

5. Engine run with header cap off to hopefully eliminate air locks.

Now the top radiator hose is hot, bottom cold. Pipes to and from matrix cold. Hose from block to matrix cold. Another flush, or air lock somewhere??Heater still blowing cold...............