Is it possible for my wife to go from Australia to the UK on a tourist visa and then apply for a settlement visa when we get there, without having to come back to Australia again?

No, I don't think so. http://www.ukba.homeoffice.gov.uk/partnersandfamilies/partners/husbandswivescivilpartners/ says you can only apply for settlement as a partner if your temporary stay was for more than six months, which is the length of the tourist visa. Australians without leave to remain http://www.ukvisas.gov.uk/en/howtoapply/wheretoapply/australia for visas through the British High Commission in Canberra, we can't do it through the Visa Application Centres. http://ukinaustralia.fco.gov.uk/en/passports/how-apply/categories-first-time-applicants/eligibility-spouse/ refers to an accompanying spouse visa, which your wife could apply for before you go, but I searched for that term on the UK Australia site and there were no results. I think you apply for that through a http://ukinaustralia.fco.gov.uk/en/visas/how-to-apply/settlement-in-uk (http://www.ukvisas.gov.uk/resources/en/docs/1903073/vaf4a is the form). http://www.ukvisas.gov.uk/en/howtoapply/infs/inf4husbandswivespartners is the UK Border Agency guidance page for partners. Good luck! Let us know when you get here and we'll have a meetup!

Gah - should read "This page says you can only apply to change to a settlement visa if your temporary stay was for longer than six months". Sorry.

Problem is, the settlement visa costs AUD$1100, hence the desire to "try before we buy" so the speak. As an aside, does anyone have any experience with the "indefinite" visa Happy Dave mentions? My wife and I have been together for about 6 years, but only married for 3. Does this mean we qualify for the "indefinite" settlement visa, or do we have to have been married for 4 years? I'd be a bit more inclined to pay the $1100 if it meant we could go for a visit, then come and go as we please after that (which doesn't seem to be the case with the 2 year version, since you need to stay in country to get the "indefinite" version later).

No, you must return to your country of residence and apply from there. My husband's just applied and we are currently waiting the requisite 2-3 months for it turn up. Processing times are nuts right now out of Canberra. You don't want SET (M) btw, it's VAF4a (updated in December). As for the ILR (permanent residence/'indefinite') you must have been married for four years. And it's a cruel joke now anyway because you still have to take the Knowledge of Life test first, then pay a further 750 pounds to get ILR endorsed. I have found the ukresident.com forums very helpful, but take the comments there with a grain of salt as there are some very anxious people posting! Feel free to MeMail me if you want more info, we're right in the middle of it now, and have other friends just about to start the process.

sorry rather the visa is SET (M) but the FORM is VAF4a

Is your wife under 30? If so she can get in on a 2 year visa with work privileges.

As an aside, does anyone have any experience with the "indefinite" visa Happy Dave mentions? My wife and I have been together for about 6 years, but only married for 3. Does this mean we qualify for the "indefinite" settlement visa, or do we have to have been married for 4 years? There's normally two levels of visa - you get the FLR (AKA the SET-M) which gives you Further Leave to Remain for two years, then after those two years, you get an ILR, or Indefinite Leave to Remain. I think if you guys have lived together for 4+ years, have documentary proof of that and got married three years ago, you may be able to skip the FLR step. Your best step is to make an appointment at the British Consulate closest to you and go and ask them.

Happy Dave - no, this is not possible. It is based entirely on marriage. And you can't make appointments at the BHC - applications are online only (or drop in at Canberra, but you can't speak to anyone).