I think I undertsand what you're saying. So its interesting that based on the wiring diagram this is the only fuse that doesn't appear to get power in the same way the fuses in the lower part of the block do, which is via the main battery feed. On the left side of this fuse a single wire connects from the panel dimmer. On the right side 2 wires exit, one to the radio, the other to the ignition switch.
I take this to mean power enters the fuse from the dimmer, does that sound right?
Andy, thanks, you are very generous! I would like to take you up on your offer to talk if that is easier. Unfortunately something has come up and I won't be able to call today. I'll try arrange something when I know I'm more available...