Mick, I removed the fuse, bent back the tabs, and gently pulled on the base. It seemed free enough away from the mounting tab, but resisted on that side. Since I don't have a spare, I didn't get any rougher than that. I will check the voltage next opportunity to rig something up - I'll set a voltmeter inside to monitor while driving.
Anything you have I'd appreciate. Email is firstname.lastname@example.org