This is one of those totally grey areas that get discussed every now and again at length with a resolution never really coming to the fore. Everyone has a different take and interpretation on this . At the end of the day if you charging people for a flight for whatever purpose then that is hire or reward . Howver if you are taking two people who are both paying a representative share equal to yours then its legal. However if the company stumped up the cash for all three of you to fly then technically it isnt . I would suggest you are fine doing what your doing , I doubt the CAA will come crashing through your door . I like a lot of others take friends flying so long as we each pay our share it deosnt matter why we fly so long as we dont earn money from it . You will probably get a hundred more responses each with a subtley different take . The main argument normally centres around the , "spare seats" thread . I would say you are okay