Update on heater blower resistor:-
It was the resistor in my case, all done and working again on all fan settings.
For information the resistor is NOT behind the glove box as a well-meaning friend suggested. To access remove the side panel (passenger side) to the centre console (one star screw and multiple push clips). Then get your head on the floor looking toward the bulkhead, then look up and 'slightly around the corner' behind the heater controls and you will see a white rectangular piece of plastic with a lead plugged in and also held by one star screw. Remove, replace and re-fix (it helps if you are a contortionist, otherwise it is not the easiest job to do) and use a torch/inspection lamp! Whoever in Ford designed this needs a good slap )