Chopjock.
If you let a child or anyone 'not qualified'...drive your car and the car gets damaged/injures someone....who gets it in the neck, then?
You've just seen rotarywise quote the law.
Which bit of the law don't you understand?
You cannot hand the controls of an aircraft to anyone other than those qualified or authorised to do so - even for some waggle time......unless you (the PiC) understand fully that for that period - you are acting illegally and you are not insured....simples.
Of course it goes on, all the time and everywhere but...........it is illegal in the UK.
Where is the confusion in all of this?