Modern British English has no gender–neutral word for someone who works behind a bar and serves alcoholic drinks. 'Barman' and 'barmaid' are clearly gender–specific; 'bar staff' sounds like management–speak and is better for referring to a body of workers rather than an individual; 'bar steward' is most often used, in my experience, as a euphemism for a pejorative term that originally meant someone born out of wedlock. The American term 'bartender' is good, but is not (yet) used in Britain.
The campaign to revive the word 'tapster' starts here!
© Haydn Thompson 2017