The name "Charlie" I believe (and someone may proove me wrong here, if so, so be it) is derived from a famous Fox Hunter called Charles James Fox. He was a wig and an opponent of Pit the younger.
Charles Fox was the son of Henry Fox who was the paymaster general, and John Powell was his secretary. John Powell purchased Quex Estate from Charles Fox in about 1790.
Charles Fox was a very keen foxhunter, and consequently was often known to his friends as Charlie. Hence the name Charlie for the Fox.
Toby I do not know where that came from.