Our PPA time, for a full time member of teaching staff, is 2.5 hours.
HLTAs get half the allowance.
ECTs get an extra 2.5 hours.
An afternoon PPA slot is 1-3:30pm.
If your PPA is allocated for a morning session, you can often choose to have 8:30-11am, or 9:30 to 12. Sometimes it's selected for you, other timetable restrictions dependent.
We always have our PPA as a block. It's never, or very rarely, split.