2003 car, sidelights not working, any ideas?

[Jorrocks]

I’ve posted this over on the Boxster forum, but as it’s the same setup as a 996, I thought I’d ask here too.
The car went in for MOT yesterday and failed as neither sidelight worked. Rears and number plate lights all ok, fuses A3 & A4 both ok. After trawling a few 986 / 996 fora, this seemed to point to a faulty light switch so I replaced it with a new OEM Porsche part but that didn’t do the trick either so I’m now at a bit of a loss!

One other thing that I don’t think should have any bearing but I’ll mention anyway, is the indicator stalk for the offside (RHD) has done the usual and doesn’t stay on, needs to be held up manually to work.

Any advice gratefully received!