The English accent just puts it inline with the first Sands of Time trilogy of games. The voice and accent definitely worked to reflect the Prince's sophistication and pompous attitude, almost having a stiff upperlip.
Nolan North's voice talent came in with the most recent installment, in which the Prince's character was notably more aloof and laid back. North's voice is famous for portraying that sort of character i.e. Nathan Drake from Uncharted among many others.