Have you seen the George Sanders films?
Sanders doesn't really look anything like my concept of Simon Templar (much too physically square and powerful; his heavyweight bruiser physique always seemed at odds with his aura of palpable intelligence), but he's a great enough actor to nail the *personality*.

Dalton is much more my image of what Templar looks like, and based on his Bond and 'Errol Flynn' I think he could do the personality as well.