The only thing which protects ops staff, is the EEC WTD (working time directive).. It’s a long document which you should find on the internet.
Couple of points I can remember:
1. An individual should have a least 11hours undisturbed rest.
2. An individual should not be rostered anymore than 48hours in a 168hour week. (Overtime is at the individuals choice and is therefore not rostered)
Don’t think there is any rules regarding working alone on nights, security jobs come to mind..