Your subjective assestment of these divers as presumably representing the top 1%, aside. Is GUE actually teaching helium usage to students it feels aren't qualified to exceed 60 ft.?
Provisional triox students were advised not to be below 60ft. As in "not yet meeting rectriox standards"
Since the Channel Island charters tend to be shallow (20-60ft) and air diving, I'd be surprised if they require anything beyond an OW card. The one cattle boat I've been on down there didn't want to take us to the oils rigs. Too risky being without a bottom and all