For the most part, the transition from Australia to the UK is usually fairly straightforward - apart from the stark contrast in weather of course. Culturally, the two countries share a great deal and then of course there is the convenience of a common language. You can count on some friendly banter between 'Poms' and 'Aussies' and generally Australians in the UK rarely feeling like outsiders.
It may therefore be unsurprising to know that on the whole, the law and legal systems in Australia and the UK are incredibly alike. Both are based on a fundamental belief in the rule of law, justice and the independence of the judiciary. Of course, given the historical background between the two countries, there are enormous similarities in the underlying development of the two systems. Namely, both are based on common law, which primarily means that judges' decisions in current cases are based on the precedent of rulings in previously resolved cases, an effect of which can be seen in Australian law. British law has had a major impact on the Australian legal system and the direct influence is apparent through legal resources such as Legal Vision, where information can be easily accessible on both ends.
There is however, one major structural difference between the two legal systems, one which may have an impact on the way you relate to the law in your life in the UK. In the UK, there is only one parliament and it is the sole body responsible for creating legislation. However, in Australia, there are essentially nine different parliaments and each one of them can make laws - There is one federal parliament, plus eight state or territory parliaments. Federal law almost always overrides state or territory law. However, this multi-faceted system means that different laws apply to different parts of Australia. So for example, when it comes to traffic laws and regulations, you will often find that the exact specifications differ from one area to the next. As an Australian, you will likely be used to these variations and so it should not come as a shock to arrive in the UK to find that there are also individual idiosyncrasies there too.
So, what are the disparities that you can expect? In short, not a great deal. However, there is a general perception that there is greater leniency in the UK regarding speed limits. There are some other quirks too. Although not law, you may find that if you want someone back home to send you certain items, they may not be allowed into the UK by the Royal Mail. For example, some strong Aussie alcohol may be prohibited. Meanwhile, the same could apply to especially high performance electrical items such as specific laptops.
Perhaps the legal area which is most worth paying attention to though, is the UK's relatively new regulations on immigration for spouses. A couple of years ago, the UK made the requirements for obtaining a visa more stringent. The new regulations stipulate that the British citizen themselves must already have a UK income of at least £18,600 in order for their spouse to even begin the application process. That spouse must then serve a probationary period of five years before being granted permanent UK residency. It is worth paying attention to these rules, as they may well impact your time in the UK.