Help! Lights not working

Right can someone please tell me what has gone wrong with my Landy Disco 200tdi TDI this time.
Its running fine but i have no dash lights, no main beam at all side or full, no back lights (brakes and indicators are fine) and no interior lights. I have taken a look at the fuses and they are fine.
Any ideas and if so what do i do about it just so i can get her working for yet another month LoL.
Any help thankfully received

Including fusable links? also a faulty light switch will give you the problems.

Main Fuse 4 in engine bay fused box
Other than that, get a multi meter, or get a bulb connected to 2 wires with croc clip on one and a nail on other
Then working from a bulb find a connector and check for power, no power find next connector. Keep working back to switch, then switch to fuse box, fuse box to battery until you find electrons coming out the wire. Process of elimination

This way you can trace where the fault is for all cicuits

Thanks for all your replys, it turned out to be the main fuse wires had corroded and split so after a simple clean up and reconnection everything is working perfectly; for now anyways.

Tabby said:

Thanks for all your replys, it turned out to be the main fuse wires had corroded and split so after a simple clean up and reconnection everything is working perfectly; for now anyways.

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A common problem for discos of a certain age