You wont need a part number if you go to Fords. I checked these out on eBay and the genuine ones are more expensive than buying these from Ford. Should be less than £40.
There should be two hoses going into the bulkhead. One is the hot in and the other out. These will be attached to the HCV.
You need to disconnect the electrical plug which operates the solenoid.
Disconnect the two pipes going to it.
This will release an amount of coolant. Pull the HCV back to expose another two hoses which will also need to be disconnected.
Fitting new HCV is reverse of removing.
Top up the coolant with a mix of antifreeze and water.
Run engine with heater control on hot until engine runs up to temperature.
Let cool down and top up coolant as necessary.
This is from memory from changing the HCV on a Puma.
Here is a picture of a cheap one from eBay. It looks exactly the same as the original: