Ok, I'm wiring up a setup for new headlights for the car. I've got a challenge, I think I know the answer. I'm after confirmation and help finding the correct diode (unless I'm completely wrong). When I switch the headlights on, the headlight circuit is live (12v). When I switch the mainbeam on, the headlight circuit cuts, and the mainbeam circuit is live (12v). What I want to do is have the headlight circuit live when the mainbeam circuit is live (not the other way though). Below is my diagram using a diode to acheive this. I'm not sure what diode I need, or where I could source one from in the UK. Any help really appreciated.