In my time (several years ago) the groundcrew worked 24-hour shifts, I believe the last in the Service to do so. They did 14 days of alternating days on-shift and stand-by (one hour's notice), followed by 7 days of stand-down (24-hour's notice). On paper it looked good, working one day in 3, but they would often be up through the night and were frequently called in from stand-by or stand-down. Not sure if things have changed. The aircrew did the same 24-hour shift as the groundcrew but different patterns, someone else would be better to advise on this.
Slightly off-thread, anyone out there know the dates for this year's Engineers' Walk at Boulmer?
HW