I haven't changed anything. It happened after I was doing a compression test which involved lots of turning the engine over, I doubt this is related. The sidelights weren't on then but an hour or 2 later I went outside and they were.
From pulling fuses, I worked out that they'd go out with the 10amp interior light fuse (4th down on the right). Should they be on this circuit or not? Maybe someone could check. My logic was to start looking at things on this circuit. With the battery disconnected I removed the drivers door switch, unplugged it and connected the battery. The sidelights didn't come on anymore. I reconnected it and they still didn't. Unfortunately it's gone the other way now, the sidelights won't turn on at all, not even off the light switch.
I don't know what to make of it all. The drivers door switch and interior light work. If I open the door the interior light comes on.