The problem lies not in the rules, but in their enforcement.
I can't speak for the UK but in France it is not allowed for an intern to work more than 40 hours a week under any circumstances, yet in many industries you still see 60+h workweeks as a standard for interns...
Because by any means, an intern subject to this kind of unacceptable working conditions will not speak up since that would annihilate his chances to get a job at the end of his internship (and might even discredit him at other companies in the same industry)
I can't speak for the UK but in France it is not allowed for an intern to work more than 40 hours a week under any circumstances, yet in many industries you still see 60+h workweeks as a standard for interns...
Because by any means, an intern subject to this kind of unacceptable working conditions will not speak up since that would annihilate his chances to get a job at the end of his internship (and might even discredit him at other companies in the same industry)