I don't think so Peter - the M had Rotax units. A quick google search seems to suggest that the S700 was used in Triumph and BSA motorcycles? But I stand happy to be corrected!
Lots of postwar cars had these; TDs I think, and generally people find the fact they designed for the ubiquitous Lucas 7" headlamp very useful. I believe the M that Frank Ashley made famous has these lamps.