As I understand it, Astura CXT 596 is chassis 33-5142 and was UK registered 8th May 1936. The engine was 91.539. In 1952 it belonged to J G Crowther, and in 1967 to Douglas Crowther. It is a 3rd Series open 4-seater.
Attached a photo of it in 2010 found on the web I think.
Astura CYY 45 is chassis 33-5272 and was UK registered 11th August 1936. The engine was 91.1027.
In 1952 it belonged to J G Crowther and later to David Clayton and then Ron Francis. It is a 3rd series short chassis with 4-door pillarless saloon body by Farina.
Attached a photo by Theo Jansen, also from ca. 2010. I have a better one as a print, yet to scan.
Paul