Imported the original 1:20 scale plan into Templot again as I was not convinced that it was previously at the correct scale. Sure enough if drawn to scale it is approximately twice the size I was expecting. In drawing the sketch I must have use some strange calculation that lead me to believe it would be possible to design this layout to scale and fit in available space. Thought this was too good to be true.
Not sure that I can do anymore with the plan today but will have to mess around with the import options in Templot to make this plan fit space. A little despondent that the layout will not be to scale.