There's a service station on the M6, I think, which has the massage chair right next to the entrance, meaning that if anyone did use it (and I've not seen anyone yet), it would be the first thing you saw on your way into the services...
Incidentally, if you want the worst service station experience in the world, I recommend being in the first services on the motorway out of Pilton on the Monday that Glastonbury finishes at, say, 10am. It's overrun by hundreds of people who haven't seen anything resembling hygiene in 5 days... :D