if you can't find the L-ornithine, and I'm not sure why it's so hard to find in the Greater British Empire, you might try a homeopathic sleeping aid. Nelson's (from the UK) is very good. It's called Noctura. I find it at Boots in the UK, don't know if you have these in Australia. (It's available in some health food stores and drug stores in NYC -- don't know about elsewhere, in case anyone is wondering. You can very likely get it on line, though.)
Yes, the l-ornithine does mop up toxins -- specifically ammonia gas in your brain. I hope you can find the l-ornithine, but the Nelson's makes for a nice sleep, too. Follow the directions and start taking it a few hours before going to bed.