Today's BWOTD is open for gross mis-interpretation!
"Would you just leave it out"
"Leave it out" = "stop doing/saying that" or "you must be joking"
This is another real Londoner and the Home Counties phrase that I would hear on a daily basis and it often made me smile to hear it, or use it myself!
So if a Brit' ever says this to you, they are not asking you to leave anything out for them, they're basically telling you to "shut-up", "quit that" or "be serious" in a friendly/jokey manner.