Hi.  I have been reading with interest your posts.  I am currently living in Adelaide and have lived and owned property in both Adelaide and the UK.   We sold a flat in London in 2001 so I can sympathise with you on the terrible buying/selling system in the UK.    In my experience, Adelaide prices do not fluctuate anywhere as much as they do in the UK.   There is speculation that prices may drop.  The "experts" tell us Adelaide should remain relatively stable, but who knows for sure.  I guess at the end of the day you are making the move to Adelaide for lifestyle reasons.  We did the same back in 2001.  If we had hung on to the London flat for another 18 months we would have sold it for a lot more, but we didn't know that at the time and sometimes you just have to make a decision so you can move on with your life.   
KY is right in saying that properties are not selling very quickly here at all.  Bear in mind though, we have a much smaller population so things do not turnover at the same speed as what they do in the UK.  Mortgage interest rates around 6-7% which is low.  In 1989 I was paying 17% !  Our interest rates have always tended to be higher than the UK but then our houses are cheaper and you get more house and land for your money.    We have a couple of investment properties that have done well over the past few years, but I think we will see a stagnating period for a while now. It is a good time to buy and those that are desperate to sell will accept lower offers.  But I think with the lower interest rates, people are just deciding to hang on until the market picks up.

Overall, my thoughts are:  if you buy in Adelaide, be in it for the long term.  I don't think you would see a huge fall in equity, but a more stagnating effect for a few years before another boom.   That seems to have been the trend since I have been in the Adelaide property market.  Of course,  the future economy could make a complete liar out of me, but that has been my experience over the past 20 years.    You can rent a nice house here for $350-$400 per week, but the rental market is tight and it can be hard to find somewhere. 

Good luck with everything and I hope the sale of your house goes through smoothly.

Y