Just realised it's a radio script.
Hence lack of action - duh!
I think Radio is REALLY hard.
The trouble is, people hear unmitigated shite on R4 and think they'll concentrate their efforts there, reckoning it'll be easier to get something away.
Not so sure about that - especially in terms of advancing your craft
You might be better working this up for the screen - it'll certainly help keep things a little more spare.
Failing that, write the plot down in about five lines - then make sure the plot kicks off within the first ten lines of dialogue.
Keep those five lines of plot in front of you and make sure you don't spend more than four or five lines without advancing the plot.
Just cut out the gags/exchanges you don't need and use them later ( the one good thing about dialogue that doesn't advance the plot is that you can put it anywhere!)