I don't believe Heathrow Hertz has a gold service like the US so I think it is just saying that. I did try to look for you as I haven't rented from there for years now but the Hertz UK website adds a new level of amateurism to the Hertz web team. If you go here: https://www.hertz.co.uk/p/car-hire/u...athrow-airport and scroll down to

Hertz Car Hire at Heathrow Airport

and try to select, for example: Collecting your hire car from Heathrow Airport then you will end up at what looks like someone called Joshua Hartley's sharepoint work in progress! Oops!