I thought, rather than start when we're on holiday, I would also blog how I've prepared for this trip. Maybe someone will find this information useful.
First off, seeing what accommodation is available.
I had a look at youth hostels http://www.hihostels.com/ but found they were more expensive than I expected, from about 21 Euros a night for one person and as the pound is so weak at the moment its more than I can afford.
So we've decided to camp. Camping looks as though its going to cost about €9/night/person. Found some campsites at http://www.europe-camping-guide.com/en/list/austria/salzburg/ and http://camping.salzburgerland.com/eng/index.html
Most seem to suggest we don't have to book ahead (except peak season), but I probably will, probably save me explain in my limited German what I want when we get there. Hoping they will send me some more info that I have requested via email and then I can book.