It all depends on the policy definition of 'trip'. Unless the policy specifically states the contrary then a trip will not need to be on one ticket or in one package. The itinerary may be made up of many separate tickets and reservations across many airlines and suppliers. No need to worry about exEU itineraries as each 'trip' will commence from the UK (for those resident in the UK) notwithstanding the short positioning flight on a separate ticket.