Trial Lessons at HGFC are exactly that - a lesson. A full pre-flight briefing is given and the person having the lesson is told that they will be operating the controls to the extent that anyone having a first lesson would. The flight is always with a FI. I would have thought that removed any doubt about the nature of the flight.
As for me, my first (unofficial) lesson, with a FI who did it as a special treat for me, was in a Seneca.
I later went on to learn at a completely different FTO as that one didn't have an aircraft suitable for me to learn in.