I saw one of these beauties when I was down under about 10 years ago. Its called a Huntsman spider, totally harmless. It was on the inside of the car door, it scared the hell outta me (I was only 8 at the time)
I also saw a black widow, and was dragged inside the house after spotting it :(
That's actually a myth. House spiders (for that's what yours is) live inside all the time, and only a very few ever venture outside. These spiders have evolved to live in places where there is very little food or water, and can go for weeks without any liquid intake. That's why they are often seen trying to get out of the bath - they went there in search of the small amounts of water that can linger around the plughole, and they can't get back out again.
The myth that they come inside for the winter probably arose because at this time of year the spiders are mating, and what you see in the bath, and scuttling across the floor are males on the lookout for a mate.
They are completely harmless, and are an asset to any home - they eat the insects that you really don't want in any number. Leave your spider alone - he'll not have long to go in any case; once he finds a female he'll hang around her for a couple of weeks, mate with her several times and then die. The real myth is that the female kills him - she certainly eats him, but he dies without any help from her. Let him enjoy his last couple of weeks of life.