Which of these actors/actresses appeared in the most British comedy 'Carry on...' films?

Kenneth Williams (25 films, and co-presenting 'That's Carry On!') played a range of character types, nearly always a lead character. Early roles were rather strait-laced; he then sometimes played his snide character: quite slimy and smarmy with a distinctive nasal voice.

Later the haughty, proud and easily outraged elitist became more frequent and Williams' best known character type. Williams sometimes played characters of other nationalities, such as in "Up the Khyber". In some roles, when not actually playing his role in snide mode, Williams might deliver a single joke using his snide voice. A running gag in many of the films was that Williams' character would be embroiled in an extra-marital affair with that of Hattie Jacques—this plot device was used to greatest effect in the hospital-based films, which gave rise to Williams' famous catchphrase "ohhh Matron!".

Joan Sims appeared in 24, Sid James in 19 and Barbara Windsor in 10 of the 'Carry On...' films.