Even with the most meticulous planning, things can go wrong! There is not much you can do about a change in aircraft or delays caused by volcanic ash! Consider what is particularly important to you if there’s a delay and consider your contingency.
Do take your own pump (fully charged) as this will be needed for your journey. Also, take voltage adapters (easily purchased in High St stores for a few pounds) as you will need to charge your own UK pump for the return journey. It will also be a back up should the pump on loan fail. At the end of your holiday, pack up the pump in its original packaging & arrange collection by the company from hotel reception or other mutually agreed collection point.