That museum in Porthcurno is SO INTERESTING. History and hands-on demos and then bam! here's how the big boys did it during the war. Industrially. In a cave. Very neat.
Is that at the World Heritage Grimeton Radio Station on Google Maps? https://goo.gl/maps/wfGRv7QfNtTY33iz7
That it is. Most impressive site, and if you have the faintest interest in communications and technology, you can easily spend hours there. If you're adventurous and there at the right time, you may even get to climb the masts.
That being said, I believe it is fair to say that I had a better experience than wife+kids at two of my favourite niche museums - the Grimeton spark gap transmitter in South Sweden and, all-time favourite - the museum of submarine cable in Porthcurno, Cornwall, UK.
Everybody loved the Ramones museum in Berlin-Kreuzberg, though.