This is a favourite of mine. Rita is uncredited in the film titles but it's a great little scene. Standing at her street door with key in hand she gossips about her neighbour (Barbara Windsor) to the young couple knocking on the door "I should knock if I were you, that bell ain't ringing" she quips. 

The scene cuts between Barbara, inside the flat, and Rita, outside in the corridor,where she quips, "Aw she's in alright, she don't have nothing to do. Don't have to collect the kid, it has its dinner at school".
More knocking and as the scene shoots back to the apartment then out again to the landing, "They're in alright, try again", Rita eagerly quips. "I saw him come in five minutes ago. He's on spreadover, he's a bus driver. Had his uniform on". 
The scene zooms back to inside the apartment and then back out again, at this point Rita's standing next to the couple near the door, she can be heard inside the flat as Barbara tells her to mind her own buisness, and calls her an "old gasser".
It's a smashing little scene and a pity she wasn't used a bit more by Joan Littlewood throughout the film. It would have been nice to see her in the pub with her old pal Arthur Mullard! 
The film is packed with character actors, and Queenie Watts gives us a jazz tune in the pub. It is also notworthy as the last film appearance of the late great Edie Martin