headlight goes on and off & other stuff

Having a few issues,looking for some pointers please where to start - 12v AC
1) 1st one has been like it for 12 months or so,hasn't really bothered me too much but I am wondering whether its all related
.If I don't have the lights on when I press the brake pedal the speedo light goes on.
2) Headlight is flickering on and off ( I don't mean tickover flickering) especially when you rev it it goes on and off, checked the connections at the back of the bulb holder all seem OK.If a regulator was breaking down would it show these symptoms or is it a case of it either works or it doesn't.
Any help or advice gratefully received.
1) 1st one has been like it for 12 months or so,hasn't really bothered me too much but I am wondering whether its all related

2) Headlight is flickering on and off ( I don't mean tickover flickering) especially when you rev it it goes on and off, checked the connections at the back of the bulb holder all seem OK.If a regulator was breaking down would it show these symptoms or is it a case of it either works or it doesn't.
Any help or advice gratefully received.