The spikes can be clipped with Zeners, if they are as short as you say, or Transorbs should be fast enough. The dropouts should be smoothed by decent reservoir caps anyway, and they will help you filter off the high voltage transients too, since you can't charge a Cap at an infinite rate from a real source. Full cycle drop out, or even multi-cycle mains dropouts are much scarier, and European testing must include tests for it !

Steve