i think you might have got the class of lifeboat mistaken, or the scale, Colin……..as the only 1:12 scale Barnett class hull and cabin set thay i know of is one I produced of the Mk 1 "Stromness" class 51' Barnett.
Models by Design did do a Barnett mk 2 52' Barnett, but this was either 1;16th or 1;20 class and was about 37" long.
This is what the 1'12 scale 51" long Barnett looks like.
https://www.youtube.com/watch?v=6IPGqapDrm