The HGV world is odd in that drivers with no experience are few and far between. Companies like experience not just of roads and bridges and driving, but rules and regulations too. Be prepared to spend nights in the cab (summer is too hot and winters are cold even with heating). Even though you only want 1 day a week, you will be asked for more of a commitment.
Depending on the work, you can earn up to £200 a day. A HGV licence costs money.
As for using this in Australia, that might come as a shock due to the distances and 1 run being a 2 week journey. The trucks are probably better though.
Work is there though as road haulage is the cheapest way to move stuff around the UK.
If you have no friends and a cheap place to live, I highly recommend it as it won't require much of a lifestyle change and you can earn a lot from it by mostly sitting down.
My background is as a general haulage transport planner and in 5 years, I never met a new driver.
LGV covers 7.5t trucks and multi-drop (so ideal if you want something local) and you are best off with an agency if you only want 1 day a week. You would ideally need to be physically fit as you will have no idea what you will be carrying and there is a very high chance that you will have to lift off the truck yourself.
Pay is usually around minimum wage and you can expect an hours notice of work.