with all the lights and the horn going that will just drain the battery, a good battery shop should test the battery for you, if i were at my shop i would, although it is in kalgoorlie.
they'll have a battery tester that can test the cca (the guts) of the battery although your battery would need to have a full charge,
it's best to charge it on an automatic charger and leave the battery to float before you test it otherwise you'll get a false reading.
also depending on the size of the battery, the size of the charger and how discharged the battery is it will take more than a night.
i reckon it's the alternator