It may be different across companies and depots, also different for freight.
Southeastern just had a part time shunter job share available. It was adverstised as 2 days on with 6 off. 10 hour shifts either 2 days or 2 nights. I would imagine that as a full time position it would have been 40 hours a week or 4 days worked - which is typical for full time hours with unpaid breaks. Driver's hours are worked out across the year, meaning they don't always work the same hours each week. Drivers also have to deal with delays and cancellations of their train - which may alter their weekly working hours. Shunter drivers look likely to be on set weekly hours and days.
ASLEF THE TRAIN DRIVERS UNION policy on working time for Train Drivers. Length of weekly working time: 44 hours maximum for each seven day period. 35 hours maximum per week on average over a 52-week
