Cazalet33, I suggest you read Gordon Vette's Impact Erebus. Have a look at the diagrams on page 46 and 47. If this crew was on the ball, and they thought they were going down McMurdo Sound, why was it not noticed they were on the wrong side of Beaufort Island? Met conditions at that point were certainly VMC, there are passenger photo's retrieved from the wreck clearly showing Beaufort Island.
Prospector, have a look at the photos on page 68,69 of same book for an explanation on the lack of slighting of Beaufort Island. In particular the photo bottom of page 68, those two black masses. One is Beaufort Island, one is a break in the sea ice, can you tell them apart?