One of the nice things about prepping for conventions (in this case the excellent UK Games Expo), is it gives you time to focus on a single scenario.
I’d been considering a more detailed introductory scenario for The Filthy Dozen since its release and the result is The Gonnes of Nava Rûn. And yes, this is inspired somewhat by The Guns of Navarone. It’s for 6 players, though you can tweak it for fewer. It contains enough side-tracks and random extras to keep your goblins entertained for a few hours.