A character mentions a scene in the film 'The Great Escape'. As that film was released on 1963, that places this episode no earlier than that.
For non-British audiences: a teasmade is an automatic tea-making machine typically placed by or near the bedside, and which includes a built-in analogue alarm clock which sounds when the water is sufficiently heated. They enjoyed their greatest popularity between the 1960s and 70s but are still available today.