In reply to Enty: I think you are correct, but caretakers were not checked at the time, also he applied under a false name, which was not picked up.
In any case his contact with the girls had nothing to do with him working at the school, they came to visit his girlfriend. Which nothing but an insane extension of the CRB system could possibly catch, especially with the cunning of genuine paedophiles (as against those unfairly fingered for this by hysterical over-reaction and moral panic). Moral panics often (or even some would say mostly), have some basis in fact, but are gross over-reactions, frequently for dubious motives on the part of those instigating the over-reaction.
Actually there was a great deal of suspicion around Huntley, but none of it proven by convictions, which does seem quite like the situation with Jimmy Saville (usual caveat - assuming there is any merit in the accusations of Saville).