I hear you Nev
But, I think it would be a MESSY few years of legal fighting to prove you were in the right. In that time, you would be stripped of your guns while it is decided. Because our guns (same in NSW?)have to be stored in a safe, preferably with a trigger lock, with mags, ammo, bolts etc stored locked separately elseware, It would be hard from a legal standpoint, to explain how the BG broke in and within 30 seconds you had pumped him full of lead
For example, If I were woken up in the middle of the night by the front door getting busted down, I know it would take me up to a minute to get my safe open to get the Glock out, another 30 seconds to open the other safe & get the mag out (Have 5, one mag is always loaded with 7 rounds) So being realistic, it is really not an option. However, should a person be norty and have their gun under their pillow (just in case) and they shoot the intruder 20 seconds after he smashes the door down, you would likely be charged with not storing your firearm in a correct manner, which leaves you open to being charged with illegal use of a firearm?
Do you see what I mean? Yes you would have saved your skin, but life would be hell (and you would lose your guns)
It is the same in your car, if you get pulled over for say speeding or breath testing, and the cop see's you have a baseball bat/large screwdriver/tireiron next to the drivers seat, you better not say it is for PROTECTION, you can get charged for having a weapon in reach of the driver, and then you loose your guns (that are at home in the safe)
Summing up, yes you might end up defending yourself with a gun here, but it would depend on circumstances & whether your 'trial by media' supported your legal case, or went against it
It would not be an easy time, and you wouldn't be able to get your guns back until the court case was over. If you get charged with ANYTHING, you wouldnt get your guns back.
If the above scenario happened to me, I think I would bail up the burglar with my gun, but beat him to death with a golf club or the like, and deny getting the gun out at all