I think if you are super organised, it would be great. You'll need two witnesses anyway, so are there 2 people in the UK that you can trust to help you with planning and keep it a secret?
They could maybe visit venues and do Skype tours with you so you can ask any questions you want?
Most things can be organised via email, so I think that would be fine. Are you planning any visits over the next year? That way you can at least meet your suppliers face-to-face once, and maybe organise a food/wine tasting?
Because you live in Australia, if you set it up as a big event - maybe for a special anniversary, or one of your birthdays - people will make an extra effort to come.
Give people whatever dress code you like. You can buy your wedding clothes in Australia, and just bring them with you, so that's no trouble.
Sounds exciting - good luck! X