Dear Mike,
Firstly if you have an Article 50 card and are therefore legally long term resident in Austria covered by the WA then you may buy and own property in Austria on the same terms as an Austrian or EU citizen. This does not of course mean that you can necessarily buy a second property in a holiday area where there are restrictions on all such purchases. When we bought in Bad Sauerbrunn we had to make a declaration that it would be our Hauptwohnsitz. Of course this is also in our interests as we do not want to see properties around us bought up as holiday homes. The last thing anyone wants is an Airbnb neighbour!
There seemed to be an understanding that you cannot necessarily move instantly from one house to another (in that respect the system here is quite unlike the English buying and selling “chains”).
That said, not all Notar are well informed. Nor are those in local government. At one point we were asked by one local official if the UK was a member of the European Union. There also seemed confusion about whether it was still necessary to produce evidence of marriage to an Austrian and we were asked for our marriage certificate even though this was not strictly a requirement.
As a general point I would not rely on a Notar. They can be Dickensian. We depended very heavily on a good lawyer. You will need a Notar for some stages of the purchase but generally speaking I would strongly advise you to find a good lawyer who is experienced in working with the international community. That can’t be very difficult in Salzburg. The right lawyer will know that you do not need to ratify the purchase as a Brit if you are covered by the WA. Many lawyers will offer you a global rate (about €5,000 + costs) rather than an hourly one. Then you just pay the Notar the very specific costs for notarising certain documents and these costs are all set out in legislation and are relatively small. But in my view you should NOT rely on a Notar to look after your own interests.