What are the maximum hours a night worker can be expected to work in every 24 hours?

Most workers who normally work at night are protected under the Working Time Regulations, (including regular rotating shifts, but excluding those who only occasionally work nights).. Night work is defined as at least 3 hours work taking place during the hours 11 pm to 6 am. Over a reference period of 17 weeks workers are not required to work more than an average of 8 hours on night work in every 24 hours (eg 48 hours per week over 6 working nights). An exception to the average is where night work involves special hazards, heavy physical or mental strain. In these cases there is an absolute daily limit - work cannot be continued beyond 8 hours in any 24 hours. For some workers, (for example, security guards, caretakers, and those doing certain jobs which cannot be interrupted), the regulations restricting the length of night work to eight hours do not apply. As with day workers, night workers are entitled to at least 20 minutes rest during any period of work lasting 6 hours or more.

You cannot 'opt-out from these nightwork limits.

There are different rules for mobile transport workers and tougher rules for 16 and 17 year old workers.