Bongo Fury

Ok, after messing about with the instruments, as I was swapping the speedo for a MPH GA5R one, my glow plug light is constantly on

Doesn't affect start up and Bongo is running fine.

Any fuses to check?

Ta

It won't be a fuse problem. Sounds more like a wiring short or something odd, given that you have replaced the instrument panel it sounds like you need to take it out again and check for any incorrect connectors or shorts on the flexible PCB track etc.