Er, it's stating the bleeding obvious but the answer to the first question is in the same sentence. No, there's no chance whatsoever of a sentence if there's NO PROOF as you say. The law in this country requires proof before conviction (certainly before criminal conviction anyway).
As for the second, I don't know enough about it but I would imagine it would depend how much money is relevant. I doubt it would see jail time for a first offence of minor amounts. And of course there will be no sentence without a charge and no charge unless they've actually been caught working on the side. Have they been? You don't actually say.