Hi, one of the way to spot the difference is that the Magnetic ballast is far heavier and also get very hot compare to a newer digital system. also is the price you have paid, a good branded magnetic sell for around £60 but you can double that for a digital.
When you plug your ballast, does it become hot after a while? if that was only the light bulb or the cabling after the ballast it still would get hot. if not and you have changed the fuse in the ballast plug then it might have just died on you mate. hope that you resolve the issue quick, good luck