Thanks for the replies.
Combining the Transiting Flight from ETC’s suggested CAP493 along with the Shoreham’s Over-flight format I’ve got something I can use to get people thinking about the person on the other end of the radio.
Part of the problem is that most of the people I fly with for the instructional hour are operating from farm strips. Safetycom is about as far as most of them feel comfortable, possibly A/G at Headcorn where they get to see the guy on the radio when they go in to pay the landing fee. Farnborough LARS covers the area and some of the more advanced ones will talk to London Info to open flight plans etc. It’s a case of getting them to feel comfortable and confident to talk to ATC. As mentioned above, I think the Visit ATC days is one of the best initiatives that has come along in recent years.