Right i'm trying to get a few details together befor I go ahead and do a small mod or 2!

Wiring up a pair of extra sidelights on a seperate switch from the normal headlight one:-

Wiring like this??

Batter positive, wire to a fuse (20 amp?), then to switch, from switch to sidelight lamps then to earth? (does it have to go back to battery negative or can i just earth it?

Just want to do something slightly different!

Shell is negative earth mate - you simply connect switch,fuse battery and lamp along a positive line,then earth each end to the body.

So why are you using a seperate switch,instead of doing as I've done and linking them into the existing sidelight circuit - you fitting dogging neons?

You'll have to see them at the show! No neon's! Maybe some funky LED's though!