Like others, I have sometimes wondered about the Jolly Club. Reading the material linked above, I am little wiser! I can only conclude it is some very Italy-specific entity that does not equate to anything in the Anglo-Saxon world. It seems to be a lot more substantial than, say, Ecurie Ecosse, yet it doesn't seem to be a substantive body like Prodrive or Joest Racing. The pdf file that Vitesse2 posted mentions F1 as well as providing engines for series from F. Junior up to F1. Anyone know anything about that?
Re the name, there was an odd little fun car called a Fiat Jolly - an open top sort of beach car, sometimes with a stripey awning. Maybe the word 'Jolly' has that sort of connotation in Italian. It is just as well that, back in 1957, they didn't decide to call the Gay Club.