I'm reasonably relaxed about this Tom. My Roadster has the main bank of fuses on the bulkhead. Recently I pulled them (eight) and just polished the contacts, which were slightly tarnished.
The bank of twenty fuses under the dash is hard to get at so I only go there when I have to, such as when the horns stopped working.
The single main fuse in the rear cavity I would only check if I was in there.
Thanks Dave. I just realised I hadn't acknowledged your response so apologies for my bad manners. I've realised that this is probably also a feature of my other cars so the only issue is that the fuse may be less protected in the Morgan due to it's traditional construction. I would worry about completely covering it in any way that might trap condensation, so I think the preventative measures are to ensure it is reasonably shielded from dirt and water and then inspect it once or twice a year. Interesting though that protecting the car's electrical circuit might put the occupants at risk if the fuse pops at the wrong time and place!