I've had similar problems in the past. On one occasion vehicle started but lost all electrics whilst driving (no indicators, speedo, lights etc.) Luckily it was daytime.
Changed fuses etc. on several occasions. Turned out main fault was a faulty/broken electrical cable which had chafed in the wiring loom. Dealership fixed the broken cable but weren't too helpful.
m.b.s. you wouldn't happen to have a Renault Trafic, Nissan Primastar or Vauxhall Vivaro by any chance would you?
Dave