I have seen R22 pilots with PPL's and 4 bars who describe themselves as "captain" wherever they go, and AW139/S76 captains with 20,000 hours and no bars and no name on their flight suit who describe themselves by their first name.
my own view is that for single pilot ops it doesnt mean that much to call yourself captain although I guess its technically legit I would be happy to be called "the pilot" in that context, but for multi crew its more valid to describe yourself like that so the passengers and operations and others involved know who's in charge and ultimately responsible from the crew.
as for bars why not wear them when your doing the job only, there really is no need to walk round tescos wearing them, although some people do, i guess they have a need to be respected.
CF