Disco 2 dash/instrument illumination failing only on dipped headlights

Ok, slightly bizarre one and I can't find any advice for my exact problem (sorry if I'm missing it; i have tried searching).

I have a Disco 2, TD5, 53 plate. When I turn on the side lights everything works as expected including the dash being illuminated and the relevant buttons etc. However when I turn the stick to the second click for the dipped headlights, the dipped headlights come on, the side lights go off and all the dash/buttons illumination goes out. On main beam, I get main beam, dipped headlights, no dash illumination. If I turn it back to sidelights it all comes back on again as expected. All the time the rear lights are working fine.

I have checked all of the normal fuses and can't find any blown.

Anyone got any ideas or had this problem before?

It sounds like a replacement switch stalk could be required.

It's a voltage drop due to load which means bad contact on the feed or earth, take ot fuse F3(interior fusebox) and bend a bit it's legs to be sure it's well connected and if no joy i'm afraid you'll have to replace the fusebox