Ford Ka question.Coil pack supplying power to spark plugs?

It could be. However, that vehicle reports trouble codes to an attached diagnostic terminal. Your mechanic should show you, immediately on demand, the computer printout where the car says it's the coil pack. There are few issues with today's cars that the car won't report the problem or secondary symptom. I would feel better seeing the diagnostic readout from the car - especially while attached to and communicating with the car. If you suspect any possible scams, just take it to another shop or parts store for a diagnostic reading - usually for free. If they confirm it, you can rest easy.