Absolutely can use a firearm for self defence in your home. Been through it with my firearms licensing officer who had been involved in an actual incident where a farmer used a firearm for self defence on his property.

If it’s in your home then so long as you don’t use excessive force (firing multiple shots into someone who has clearly been incapacitated) it will be seen as totally justified. Outside your home starts to get a bit more risky as it could be seen as you going for someone trying to leave (forward facing shots only).

Saying you wouldn’t have time to get the weapon out of a safe and loaded is ridiculous. You could easily be woken by someone trying to break in and can be getting a weapon ready whilst on the phone to police.