Issues such as national debt only influence local prices when debt gets out of hand – look at Zimbabwe and Venezuela for example. There are so many other factors involved.
UK house prices are surprisingly buoyant despite all of the current uncertainty over Brexit. Countries can have very high debt and not be hit by financial crises if the world’s investors think that the place is a good bet. Another factor that influences asset prices on an international level is currency exchange levels.
By selling your property in Australia and buying a place in the UK, you are making a currency trade. It sounds like you are going to be coming back in a few years and so you will be working through the currency market in the other direction as well.
In your case, the currency market will be a bigger factor on your profit or loss than the influence of the UK’s debt on property prices. Things are getting even more complicated at the moment because much of the world seems to be moving into recession. The debt of each nation is a big factor when an economy is shrinking,
Both the UK and Australia are expected to avoid recession over the next few years and will both grow at roughly the same pace. The UK coming out of the EU will likely grow its economy faster and the positive noises in the UK over trade deals with Australia means that we will probably do very well out of the move. The two economies seem to be moving in synchronisation.
So, national debt won’t lose you money on your property investments. The British pound is very depressed right now because of uncertainty. Once the UK leaves the EU, the pound will shoot up. So, by moving your money to the UK now and then moving it back in a few years, you will make a profit regardless of whether you put the money into property or just park it in a bank.