Would it seriously be classed at 'working for MI6 if he was simply passing on information that he uncovered as part of his usual journalistic investigations anyhow. He wasn't paid by them, just passing on any info ie "the true level of any horror that was going on in there" and "nothing to do with security" and all they wanted to know was if it was true there were dying children.
IMHO they just made use of someone who was in there and able to report the situation to both media and MI6 isn't actually working for them.
If so, then I work for BTw, BT Openreach, Plusnet, TP-link etc etc etc.