Hmmm, without wishing to be a scaremonger, if you've got a constant 5a drain, (got that from the other thread), you may find you've got a high resistance short circuit somewhere. If it's enough to flatten your battery in a couple of hours, my guess is that a wire somewhere could be shorting out and either lighting a bulb, (some bulbs), very dimly or the wires getting very hot and will soon start to melt stuff.
This 'could' cause you a major headache requiring the assistance of some burley men in uniform, a big red truck type thing and some hosepipes....
Now, what ever floats your boat, but personally, I'd recommend disconnecting the battery when the car's not in use and get it to an auto-sparky asap.
Whilst your driving the car, make sure you have the tools required to disconnect the battery quickly, just in case.
Sorry to put the fear of God in you, it could be something really simple like a duff fuse, (I've seen it before), but better to be safe than sorry.
The fuse for the sidelights and dashlights is combined and is in the kickwell. 10a (red) by memory.
Using your multimeter, check the related fuse with the lights switched to the on position. You should be able to put the positive probe on both sides of the fuse. You should have 12v on both sides. If your 5v reading is on one side whilst 12v on the other, change the fuse to start with, (don't be tempted to uprate it!). If changing the fuse does nothing and you still have 12v on one side and 5v on the other, if this is where your electrical knowledge runs out, disconnect the battery and grab the Yellow pages.