Yes, the problem of 'hidden hours', is rife in the sector in which I work. For example, I may be allocated 10 projects a week which pay £10 a project. They have to be completed and returned within 5 days of allocation. If each project took 1 hour to complete, then I would be working for £10 an hour for 10 hours a week, which is not bad for part time work. However, if the projects take twice as long, then I would be working for less than minimal wage. Add to that the fact that the work has to be detailed and professional and that people who work on the projects must be education/industry specialists, and you get into the realm of the ridiculous.
In another role, the rate of pay is £12 per hour, again 'workers' (we are not employees of the company) have to be post-graduates. The work is fulfilling intrinsically, but deduct from the hourly rate the cost of travelling 30 or 40 miles on public transport with no travel expenses, and the hourly rate is reduced significantly.
One may ask why people take on such roles and another lie is revealed. Like many other 'freelancers' or 'zero hours' workers, I took on the roles because it offered the flexibility to fit in with caring responsibilities. However, I cannot dictate how many or how few hours (or projects) I will work. If I 'refuse' three assignments, my 'agreement' (there is no contract of employment) is terminated. Under such agreements, I have no sickness or holiday pay either.
If I added up the hours I work in the four part time posts I have undertaken, they would exceed the maximum stipulated under the EU Working Hours Directive. However, how many companies will care about that after 31st October?