Sally-Jane Spencer had retired from acting to bring up a family, but returned to reprise her role as Linda
Due to her long-running rôle of Audrey Roberts in Coronation Street (1960), Sue Nicholls only had a very limited amount of free time to reprise the part of Joan, hence why the character vanishes for much of the series.
Reginald Iolanthe Perrin's headstone shows he was born in 1924 and died 1995.
Following his final reprise of Tony Webster in The Funny Side of Christmas (1982), Trevor Adams retired from acting to become a solicitor. Despite this he had expressed a definite interest in rejoining his old colleagues for this series. Sadly his legal commitments left far too little time for him to do so; Tony is therefore largely replaced by Joan's new lover Hank Millbeck.