This is very valuable feedback. I had thought a Scot/Brit audience would have cottoned on to this one, but it seems I was right to be wary.
I posted this on a US site and whilst the gag went down well visually, they certainly didn't get the punchline.
Sometimes the colonials hold onto the vestiges of the Old Country longer than the Old Country does.
I'll rework the punchline and test some alternatives out on you, if that's ok?