The answers to your questions are somewhat complicated Alex but I'll try my best.

Before everything went to hell last year the worlds financial system was humming along quite nicely, people were borrowing money in one country and investing it in others, there was a commodity boom going on, oil was going to $140 a barrel and most other major commodities were similarly going stratospheric. This was good for Australia because oz is a major commodities producer so Australia was getting more money for its products. On the whole that's why Aussie dollar is considered a "Commodity Currency" aka a currency that tends to move in tandem with commodity prices.

Now in October everything went to hell and everyone panicked, people worldwide knew something was wrong, they didn't know how bad it was but they knew it was bad and more to the point half their investments were going sour (US Mortgages), so what did they do? They looked to see what they had a profit in, aka commodities and sold em, they sold everything they could in order to raise cash to pay off their debts, the consequence was a worldwide stock market crash and a crash in commodity prices and remembering that the Aussie dollar is corrolated to commodity prices, people sold investments in Australia and moved that money home, where they needed it. Consequently money flooded back to the UK (major financial hub) and New York (other major financial Hub). Meaning the oz dollar declined against the pound and dollar in that massive spike you see.

Now the spike deflated back to where it started and then bounced again a bit in January, that January spike was probably just technical (I'll explain that below) and then the pound continued to weaken against the oz dollar and has continued to do so for the remainder of the year the reason being that once people had caught their breath and realised that actually the world wasn't going to end, they looked at the worlds economies and realised that China was still going and if China was still going there would still be demand for commodities which oz would supply, they also realised that Australia wasn't even in recession yet and the UK and America were, so they decided there money would be safer and get a better rate of return in Australia because Australia had a better economy.

What it comes down too in the most part is that money is attracted to two things, higher interest rates and sound economies, OZ has a good economy and pays higher interest rates on balance than most other countries (historically) consequently people want Aussie dollars and to invest in Aussie companies e.t.c. Also the UK is particularly hard hit by the current recession and paying very little in terms of interest rates, we are also in the process of building up huge amounts of government debt, something that currency investors don't like. Consequently the exchange rate vs the oz dollar is going to be bad for the foreseeable future, if I were you I would be sending regular sums of money back to oz, I think your money is better off there than it is here.

Finally a note on the "technical" bit I mentioned. Currency traders in fact any kind of trader will look at the chart you posted and see alot more than a layman will, what technically happened in January was a dead cat bounce, currency traders in the end of december pushed the rate towards a major line of support while the markets were thin, in January when everyone came back to work they bought off that support line and we got a bounce but it obviously wasn't to last for the fundamental reasons I've given.

Probably alot of that bit didn't make sense but suffice to say it didn't rise for any particular fundamental reason it was mostly speculation.

If all this is leaving you bewildered there is one golden rule, the trend is your friend, look at the chart and see which direction the rate has been going, it will probably continue in that direction. As I said October was an abberation and not something you could really foresee so don't worry about it and just follow the trend, making decisions accordingly.