I will be flying on QR BKK-DOH (A380)/DOH-LHR (A380) IN October when I get to LHR I will connect to UA LHR-DEN, my question is will QR allow me to carry on backpack + small bag with wheels that would fit in overhead bin, I don't want to check a bag because I can't afford the time to leave transit area at LHR, I am aware that QR uses terminal 4 at LHR and UA is in terminal 2! Any insight on this plan would be appreciated!