that isn't the purpose of the ex 3 foxmouth if it is the start of the course.

It is for them to get acquainted with the sensation of flight and also the ground side of things.

If I was doing a zero to hero the ex 3 would take at least an hour if not an hour and half with 20-30mins airborne. Including 1 and 2

Pre flight pre brief would be the normal TF but also include exposure to techlog and paper work, airport rules and regs and ground emergencys. Flight wouldn't be to a area of there choice it would be to show them the training area and point out various land marks and of course have a bit of a laugh. De-brief on flight would be very brief mainly "did you enjoy that" then they would be sat down and the ground school and books sorted out. And have a question and answer session which the parent would sit in on if they were funding it. The student has to feel special, the parent has to trust you and there has to be a few ground rules to be set.

There is a knack of getting a full course out of a punter and unfortunately a hellva lot of instructors don't have a clue how its done,

My trial flight was similar.

Were you tired afterwards? I was. Probably means just flying about a bit was enough for me for a first flight!

This sounds pretty much like the trial lesson I gave this morning.
I was planning on having the preflight finished by the time the customer showed up but he was early so he tagged along on the preflight.
At this stage in the game it doesn't really pay off to do a very elaborate lenghthy (45+min) instructional preflight. I can't assume you have any idea what I'm talking about except for the very basic.
We went back inside for the WX brief which I briefly explained and I did a quick feet=rudder=yaw and hands=aileron/elevator=pitch/roll.
I briefed on exchange of flight controls and that was it. Safety brief and go.
He got the controls at 1500' and flew for the next 45 min, more or less straight and level doing turns solely on outside reference (see the town? Fly me to it please, follow the road etc etc)
I kept quiet for at least half the time to let him enjoy the scenery (100+ miles vis) and not overload him.
Took the controls again below 1500' and landed, taxied to the apron.
Signed up on the spot and will start in two weeks.
A trial lesson is a bit of a misnomer as it's more a introduction flight then a first lesson.
In my neck of the woods you would do an intro-flight then 4-5 hrs of ground school before you fly your first "real" lesson so you at least know what your instructor is talking about and you are not completely overwhelmed in the aircraft.