Lady
With the very greatest of respect, if the client is paying £100 per hour then punctuality should be a given.
The 'student' is probably experiencing an opportunity cost of another £100 per hour on top of the fees in not doing what they would nornally do and is being punished for being professional and arriving on time - would the instructor like to be kept waiting?
As to serving a low paid apprenticeship, most of us have done that and invested a lot of money in our education both directly (e.g. for me 1 UK post grad programme, 2 in the US and a masters degree in the UK and a globally recognised vocational qualification, all self funded - and not cheap.) I also worked long hours for peanuts in my twenties to tee up my 30s and 40s.
It is a personal decision and I do not consider instructors to be any different to other professionals in this respect - its a back loaded, risky, enterprise and many more will not captain widebodies, than will, but everyone should know the position at the start.
Also, let me point out that many instructors are also benefitting by hours building funded by the student, a main driver for wannabees.