Leave, like all other TOCs and grades, is allocated.
TPE offer 33 days leave, 5 weeks which are allocated in blocks, then 8 'floating' days to be used as and when.
Weekends vary from depot to depot, but are generally worse than other TOCs as Sundays are inside the week. TOCs like Northern have Sundays as compulsory overtime and it can therefore be gotten rid of more easily.
At present, it's something like a 4.25 day week. 5-7 days on, followed by 3-5 days off. No real pattern to it. There's currently a Rest Day Working ban in place, imposed by ASLEF, in an attempt to get onto a 4-day week.