On the last off they can get you for pretty much anything that reports after 0600 local I think and they tend to call you at the start of the contactability period. If they've given you a trip its usually allocated by dep -2 so you can check on the work computer from home to see what you've got. As a commuter you'd probably need to be in the UK on the last night off if you are getting a HSB or you might be able to come in early on the first day if given a late report trip.