Base your decision in numbers!
To avoid regrets, make calculations to take a decision, that's how I would proceed. If maths say it's not doable, then forget it and go for plan B, C or D.
It's just an example, don't know your maths:
- Cost/day/person all included on a tight budget: 20€? (2 pax x 180 days) = 5400€ = 4400 GBP (depends on countries, needs, fuel and luck)
- Cost of shipping the bike to SE Asia + OZ = 3000 GBP (be sure to bring spare tooth brushes to clean the bike in depth!)
- Cost of Carnet = 250 GBP? (no idea UK)
- Cost of deposit and bureaucracy = 700 GBP?
- Visas (was it in cost/day?) = what countries? Not expensive there.
- Unexpected works on the bike/spares sent, import duties, inspections, etc = 600/800 GBP?
- Cost of a month setting down in OZ and looking for a job (some new clothes and more?) = 2000 GBP? (it's sooooooo expensive there!)
- Back-up in case everything goes wrong or family matters force to you come back to the UK= ?
Add 10-15% to the total for miscalculations just in case.
I don't mean this is ok, just a quick example.
What woud I do? I'd KEEP THE GIRLFRIEND first (if she follows you, she loves you and it's not everyday you find a woman willing to leave security behind... and stand you!). Then, if you love too much your current bike, keep it for a while in the UK: it can be your back-up to be sold in case you need cash. Fly to SE Asia (Air Asia?), get a bike there (say a Pulsar 220, you could go 2 up), travel six months or more, but keep enough cash for Australia (don't plan to travel there yet, it'll be 3 times more expensive). Find a job, make lots of cash, save and in some time you make THE BIG BIG TRIP. You still want to live in OZ (and love your old bike)? Go to the UK and ride back to OZ. You prefer to come back "home"? Then get a cool bike in OZ (or two if you manage to brainwash your girlfriend, a hard task), ride to UK and park it next to your old bike and star breeding your stables.
Does it sound like a plan? I hope so. Most important: GO!
Best wishes and happy travels,