Hi I have never known the ignition switch to cause the battery to go flat unless that is its still ON when you take the key out. This is easy to see. Possibly the alternator if the regulator has gone short circuit, or there could be something else draining the battery which is still on when the key is out. ie. extra lights in the back for example. If you have a voltmeter you can test the alternator yourself, its quite straight forward. It could also be the fact that your battery is knackered, is it new or old, as if it is an old battery they tend not to hold charge when they are knackered.
Bigred
September 2008