Anyone got any good suggestions for where to tap a switched live to install a dashcam at the top of the windscreen?

Back of the light switch would be where I'd go. Near the a pillar so the wiring can go straight up there to the roof liner and across to wherever you want the cam. I put the cams behind the mirror so from the driving position you don't even know it's there.

Do a search on my posts and you will find some pictures of how I did mine.

 

Thread locked as plenty of other threads that cover this topic.