1. If you apply in London then as far as I know, your visa grant cannot be completed onshore. You have to leave Australia (but New Zealand will do, and your visa can be granted in Auckland).
2. The AHC London normally grants well prepared spouse applications pretty quickly (within a few weeks in most cases). You should already have sent off for police checks etc that you will need. If you apply now you ought to have your visa by April.
3. As you've been together for some time you ought to get a *permanent* visa straight away with no temporary visa hbuttles. Make sure your application has enough information to allow the case officer to grant you a permanent visa.
4. If you arrive as a tourist with the intention of making an onshore application for residence, then they have the right to refuse entry. If you get past immigration then you still have lots of hbuttles to deal with, including work restrictions and healthcare problems until a spouse visa is granted (may not be quick either).
5. Has your Australian husband got British citizenship? IF not, has he thought about applying for naturalisation before leaving the UK (for spouses of British citizens, the process could be completed in Australia, provided he applies before leaving).
-- This is not intended to be legal or professional advice in any jurisdiction
