Warranty Query - is the labour covered?

Are you talking manufacturers contractual warranty? If so then yes, labour will be covered, though of course it is at the dealer discretion how the repair is carried out. You cannot get your friend to fix the fault and then expect the dealer to reimburse the cost, they will fix the fault themselves.

For a new car, or for a main dealer used car then labour is covered, but as you go down the food chain you might get more exclusions.