I want to travel to Australia and back ( from UK) by boat - any ideas apart from very costly cruises?

I hate flying but cannot imagine wearing posh clothes every night for dinner on a cruise liner!

Buy a canoe.

See if you can get a job in the crew of a container ship. It's extremely boring, but it will get you there and they'll pay you. You'll need to have some skill that's of value to them.

Had a friend once who said he got passage on shipping vessel, apparently some will take passengers. Might be worth a shot.
I have attached one link for you to follow up on.

Hi Feebe,
You can't imagine getting dressed for dinner every night on a cruise ship? I can, but unfortunately I cannot afford it
Do you have any marketable skills such as being a dancer, musician, cook, nurse or any of the multiplicity of talent that is required to keep cruise ship passengers entertained and provisioned on a long voyage?
The ideal qualification would be a degree in marine engineering or a masters certificate, but if you can deal blackjack, run a roulette table or even make a decent Martini all is not lost.
There are two (or possibly three} alternatives:-
1) Pay for the trip yourself (not an option I suspect)
2) Work your passage (as in the options above)
3) Find a rich old guy who will finance the trip.
In the present economic climate, cruise ships are going through a very thin patch. However it may be worthwhile to send your C/V to shipping companies, explain that you are prepared to learn and work long hours for little money, and see what happens.
Another respondent suggested a container ship. A great idea if you are willing to work, but then again there is not a great deal of trade between Oz & the UK just now.
Follow your dream Sunshine & the best of luck. If you want it bad enough, you will get there eventually.
Send me a postcard from Sydney!