I wouldn't rhapsodize too much on the Arnolt's design on the design of later British cars. The design of it did not come out of the MG factory or any British design agency. It was commissioned by a mid-western MG dealer by the name of S. H. Arnolt (often called Whacky Arnolt) and designed and built by the Italian firm of Bertone. It could be purchased as either a coupe or convertible. There were fewer than 500 built an d sold. It was indeed a beautiful car, but as for its influence on future British car designs, I have serious doubts. It is not even mentioned in Mike Allison's The Magic of MG. Another one off TD model to come out of a mid-west dealership, was the Inskip four seater TD.
Cheers,