Climb Straight Ahead / Climb On Runway Heading
I have always understood that, when given with a take-off clearance, the phrase "Climb straight ahead" meant maintain the runway extended centreline (ie, adjust heading for drift to maintain the track); and that "Maintain runway heading" or "Climb on runway heading" meant just that (ie, set the aircraft on the runway heading and accept the drift).
Anyone care to confirm this (or correct me)? In the UK primarily.