Eric;

You haven't given very much info with which to make a remote diagnosis, but maybe it is enough!

Until started and the Charging System is on-line, Battery supplies ALL vehicle power ...it stands to reason therefore that a complete electrical failure is like related to it or its connections. As other posters have mentioned, assure all main connections are clean and tight...this can be directly at the battery or at one of the chassis connections (battery negative cable, or chassis-to-engine braid)...clean and tighten these first...apply ACZP for longevity. See: http://www.sw-em.com/anti_corrosive_paste.htm

Only AFTER that issue is squared away, and the electrical system is functional should you also take a look at your Lucas junk Fuseblock and consider replacing it. See: http://www.sw-em.com/gastight_II.htm

Pre Injection 1800s had only qty 3 type 3AG fuses...(poster who writes of short 25A fuse has an 1800 mixed up with an Amazon)...fuses in an 1800 are ALL specified to be 25A. Safety Note: I highly recommend changing Fuse 3 (which protects strictly the Parking lights!) to one rated at 8A.

Good Hunting