I booked through a TA about three months ago, but at the time details of the flights were not available; just “London”. First the outbound flight with TUI from LGW appeared about three weeks later and then the inbound leg with BA to LHR about three weeks after that.
Obviously, I understood that “London” meant some travelling for us in Warwickshire, and I duly booked a room at the Sofitel for the day before our 7:30am flight on 8th July from LGW, never dreaming Cunard would be returning us to a different airport some 40 miles away!
Either Gatwick to Gatwick or Heathrow to Heathrow would have been fine; but one to the other is irritating to say the least and has caused some logistical problems, as one might imagine.