Headlights come on when I open the hood

A few weeks ago my lights started turning suddenly. I'd come back later and they would work fine. I thought it was the lighting column stalk, so put in a temp switch taking over from the stalk in providing an earth. However they continued switching off. Then I happened to open the bonnet (at the front) and the lights switch on (I'd left the light stalk in the on position).
All the lights worked fine but when I closed the bonnet the lights' relay clicked off the lights again - heard the distinctive click. The under bonnet light switch seems to be the culprit as I the lights went off when I depressed the switch nipple, simulating a closed bonnet.

I'm not that good at auto electronics and can't under stand how a switch can cause the lighting relay to switch off. Can anyone explain please?

Thanks in advance

Chris

 

Thanks, I'll do that. Much appreciated