BA@LHR.
This sounds about as normal as putting milk in your cup of tea. You will have been held at the edge of the runway, waiting for clearence. Even if there are only 4 flights a day, the cabin may not have been ready, or you may have been waiting for ATC enroute clearence.
As you turn onto the runway, about 45 degrees away from lined up, it is quite normal to begin setting takeoff thrust, as the engines are normally spooled up to approx 1.2 epr, to stabilise, prior to setting take off thrust.
The other options are wait until fully lined up without getting as tight into the corner as possible, which would waste runway, or to turn as tight as possible into the corner, which will take time, and if runway length is not limiting is not always necessary.