How can I replace the heater blower resistor in a Fiesta?

The heater blower resistor on my 2012 Ford Fiesta needs replacing for the third time. I am trying to fit a replacement but cant remove the plastic screw that holds the passenger foot well trim to the centre binnacle. The screw is very flimsy but it just spins around and I do not want to damage anything with brute force to remove it.
SEVERE WARNING. DO NOT EVER REPLACE A HEATER RESISTOR WITHOUT FIRST REPLACING THE HEATER MOTOR. Resistor settings fail because there is a fault with the motor. Replacing or bridging the resistor without curing the fundamental fault often leads to overheating and a wiring fire, as in Vauxhall Zafira Bs.
Answered by Honest John on

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