I believe the Jupiter had an aluminium body but the Javelin was steel, and that's the Ford link. The body was built by Briggs Motor Bodies at Doncaster, who were taken over by Ford, and then sold on again.
The engine was originally its Achllles Heel but it was all down to Jowett, nothing to do with Ford.
It was a brave attempt by a small company which sadly wasn't a success.
Most, if not all, of this I had known but used Wiki, which seems pretty accurate, to refresh my memory.
Thanks Allan for the info about the engine, which I would have known if I'd looked at Wiki sooner!