A blanking plate was my initial idea too!

However, as the costs of say an FM radio chip, a couple of buttons
to drive it and maybe a display are going to be less than the cost
of the box it goes in. I figured that for a few pence extra, you
might as well make the blanking plate semi-functional.

I don't want anything fancy, maybe just one tuning button (search up?),
just something really minimalist! The cost in electronics is only going
to be a couple of quid, the connectors and box will probably cost the most!

Jim.