Presuming this was all booked under one trip, you will have one BP for each individual segment of your journey, 2 in total. Allow your self plenty of time, as sometimes the queue in LHR could be long depending on the time. I can;t comment on the other 2 airports as I have not traveled through them. However, I suggest you check on line the airports respective websites and get yourself familiarized with the airport layout, which terminal operates the departure/arrival of the carrier and how to transit within terminals.