BA point of view.
Lots do commute, but probably not easy if you are junior FO on short haul - there's no 5/4 pattern it's variable days on, days off.
Travel before/after duty on a working day is allowed but if commuting prior to duty you are obviously expected to report ready to work up to the full limits of FTLs....
No free flights, you pay staff rates for commuting flights, even if you do end up on a jumpseat.