It looks like you’re on your way to learning about this interesting vessel as you know the shipbuilder and the year built. I believe that Great Britain is like the USA where records from commercial shipyards often wound up at small regional museums. I would check those museums near where she was built.
Also, large privately owned vessels like this would have been classified by a classification society; for British vessels Lloyds Register. This Lloyds did not insure vessels. Instead they published construction standards and reviewed drawings and inspected construction to insure compliance with their
standards. For a well built ship, A1. If so, the ship’s classification was posted in their list. Insurers could check this when underwriting coverage. I believe that Lloyds archives includes design information for vessels that they classified.
Roger