Although Bannister appeared in a few films including Reach for the Sky (1956), Au Pair Girls (1972) and the 1977 film version of Are You Being Served?, he worked mostly in the theatre, with credits including Billy Liar and the farce Move Over, Mrs Markham. Bannister also performed in Shakespeare and was a regular in pantomime for more than 35 years, nearly always playing the dame. In 2007, he guest starred in the Doctor Who audio adventure, Nocturne.

Bannister was the youngest of three siblings. His first marriage was to Actress Kathleen Cravos in 1959. They had three sons together – Jeremy, Simon and Timothy – and divorced. He married Pamela Carson in 1982 and lived with her in Surrey at the time of his death.

In 1960 Bannister appeared on stage at the Cambridge Theatre in London in Billy Liar, which starred Albert Finney. He starred as Darkie Pilbeam, a wartime spiv, in the 1968 television series The War of Darkie Pilbeam, and from 1969 to 1970 he appeared as "Heavy Breathing" in Jack Rosenthal's sitcom, The Dustbinmen. Shortly afterwards, he was asked to play Mr. Lucas in a Comedy Playhouse pilot called Are You Being Served? and took the part in the series. It was originally intended as a vehicle for him as the average man caught up in the store full of odd characters and baroque customs but, as it developed into more of an ensemble piece, he found his role being greatly reduced as other characters came to the top. He left the role in 1980, as filming for the show clashed with a lengthy tour for a play.

In 1972 he appeared as the weak bladdered Producer of a local theatre company in Steptoe and Son, Episode 2 series 7 – "A Star is Born". He played Peter Pitt in the 1988 BBC sitcom Wyatt's Watchdogs. Other TV appearances include Keeping Up Appearances as the kitchen shop salesman, and also appeared in Call Earnshaw, Gideon's Way, The Saint, The Tomorrow People, Only on Sunday and The Avengers. Bannister played three different characters in the ITV soap Coronation Street. From 2001 he played a recurring character (The Golf Captain) in Last of the Summer Wine. becoming a regular in the 30th series in 2009, finally receiving a name (“Toby Mulbery-Smith”), moving next door to Barry and Glenda (Mike Grady and Sarah Thomas) and befriending Morton (Christopher Beeny).

Bannister died on 14 April 2011, at the age of 76, after a heart attack at his allotment in Thames Ditton, Surrey. Are You Being Served? and Last of the Summer Wine co-star Frank Thornton said that the last event Bannister attended was Thornton's 90th birthday on 15 January 2011, three months before Bannister died.