it sounds to me as if you have an electrical fault somewhere, a coil pack shouldn't fail that soon, you could go to a normal machanic, but my advise would be to find a auto electrician as this is what he is trained for. he'll be able to track down an faults (or not as the case maybe) that casued a faulty coil pack. the labour charges you've mentioned are about average for a specialist, a normal machinic would charge around £30-£40 per hour, but he probably wouldn't find an electrical fault