The video appears to have been shot in the vicinity of the
Red Pit Car Park which is about half a mile short of the high point of the pass and the and the Kirkstone Pass Inn; the car was heading south, the Dauphin north.
So if it had been seen earlier at the Ullswater end of the pass heading south towards Windermere, it suggests to me that they certainly turned round exactly as Crab says and never got anywhere near Windermere.
No doubt if the vis had been really crap at that point they could have said "sod this for a game of civilians" and made a precautionary landing in the car park to await an improvement in conditions.