Peugeot 206 electrical / fuse box issues?

Occasionally my little 206 will start to alarm when I turn off my engine. All of the dash lights will illuminate, and STOP will flash. It's usually after I've turned either my interior light or headlights off (it never happens in daylight) which is making me thing there's a trip or problem with one of the circuits? On two occasions my horn did not work. It is electrical and should work even without the battery being turned on.
Recently she's starting to alarm when failing to start the ignition (she's regularly taking 2+ attempts to start). Do you think it could be a battery problem?
I have found if you remove the HX fuse, replace this it resets the electronics. This is just a temporary solution, any other suggestions?
I know she sounds knackered but I'm not giving up on her yet!