From recent experience I would like to offer up 3 very small titbits about the working time regs:

Always get an opt out form signed by the employee - better to make it a separate form and get it signed on induction or before, of course they don’t have to and they can opt back in again, but believe me, forgetting or neglecting this and they do over the hours - HEADACHE!

KEEP RECORDS - always keep records of the hours worked - it is easy to get people to send in a timesheet to record what hours they do. Failing to keep records incurs financial penalties, if find out, and frankly it is good management to know what and when your people are working

If your people are regularly doing excessive hours - look at hiring someone else, it will mean BETTER PRODUCTIVITY in the long term and possibly less cost in overtime.