If the error you're worried about is the double confirmation of receipt, I would hold off on emailing as this can happen due to system settings. In any case, even if you were to email the firm of CVMailUK, I'm unsure what that would achieve as even though the emails were sent twice, they confirm receipt so that's not really a problem in itself. If you're still feeling worried, I think the best place to begin is by either mailing grad rec or CvMailUK and asking them if it is normal for you to receive two confirmation emails and whether you need to be concerned about anything.