Originally Posted by
emilio911
Read the previous tips from AutoSlash and you'll know what to do.

Thanks emilio911 and of course AutoSlash.
I've contacted both Hertz UK HQ and the Hertz facility at the airport who both confirmed that with the CPD that I would not face the under age surcharge at the airport.
They were reluctant to provide this confirmation in writing though.
I'll just have to wait and see.