Coolant flush MK6.5 Fiesta TDCI

Hi folks.

I need some advice on flushing the old coolant out on my daughters Mk6.5 Fiesta 1.6 tdci.

I want to do a coolant flush of the engine and radiator of old coolant and replace with new coolant mixture and at the same time, replace the thermostat housing which i believe incorporates the thermostat and CTS on my daughters Mk6 Fiesta 1.6 tdci. 

Recently i realised, i have never heard the radiator fan come on. The temp is always in the middle and we get hot air on the hot setting on the heater. The coolant has dropped over time to below the min level on the header tank. 

There is pink discoularation on the thermostat housing bolts and a bracket below it, which appears to be residue of dried pink coolant so the thermostat housing is leaking from there.

I read on here someone disconnected the wiring connector to the CTS to check if the radiator fan works. I did this and the fan works.

So now i think i just need to replace the thermostat housing which should come with the thermostat in situ.

I will get a new seperate CTS if doesn't come with it. I don't know how to check the CTS so i will renew it just in case and they not that expensive. 

Radiator flushing seems straight forward by disconnecting top and bottom hoses of the radiator although on our car, the bottom radiator hose has a weird clamp on it and i need to take a closer look at this. I plan to get some jubilee clips to replace any bothersome hose clips.

For the heater matrix, i think its a case of removing the hoses and flushing at low pressure.

My main issue is, i don't know for sure how to flush the engine of old coolant.

I have a vague idea from where i read somewhere, that after reconnecting the top hose of the radiator after flushing it, you can put a water hose in one of the coolant pipes after removing the theromostat then you can flush the engine seperately from the radiator but on this engine, i cannot work out for sure which hose it is and i can't take the thermostat out seperately from the housing if thats what they mean. 

Which hose do i follow to flush the engine please.

I think the diagram below represents the cooling system for our Fiesta car for identification.