Prado headlight failure

[Roktruk]

2001 TX 1kze ~170k. I've owned this about 6 years now, fitted with 100/90w globes and a pair of Oscar spotties just after I bought it. On Friday, about 6am, flicked the headlights on, brief flash and then nothing. Parkers and tailights still worked.

Initial investigation found the 2x10amp fuses under the bonnet in the big fuse block were blown. Replaced these, fully expecting them to pop again, but they remained intact when I flicked the lights on. I now have high beam flashers, but no normal high/low beam.

The underbonnet relay clicks on the flasher circuit, but no action when switched at the column. I've swapped out the relay, with no joy. I can jump the two big pins on the relay block and the lights work, along with the high/low switch on the steering column.

So now I'm stumped. I've checked all of the obvious plugs, connectors, relays and switches. There is some disconnect between the column switch and whatever powers up the relay in the box on the RH inner guard. I have a couple of different wiring diagrams, but can't trace the logic behind the switching.

So.....any thoughts? Anyone struck this before? The only other thought I've had is wherever the main high/low switching mechanism is, the contacts or whatever they use (are these solid state?) may be fritzed - but I don't know where this is!!

Any help appreciated,
Greg