Quote Originally Posted by spongebue View Post
In that case, you should be good - as far as I know, taxes are always charged on departure, not arrival.
Yes only on departure but if you are connecting in LHR from another airline to your own airline just ask to be considered as a through passenger and a big chunk of this taxes should be waived.
It will not work the other way coming to LHR on your own airline and taking a flight on another airline.