If you are thinking of going to study in Australia or New Zealand, you will have realised, that both countries are about as far away as you can get from the UK. Unless you want to spend 3 months getting to your chosen college, flying is really the only way. At a minimum the journey from the UK to Sydney can take 21 hours with the necessary stopovers, so it really pays to plan your travel arrangements ahead of time!
Flight prices to Australia and New Zealand can fluctuate wildly throughout the year, the most expensive time to fly from the UK and Europe is around Christmas (which is summer Down Under) but prices will also go up throughout the main European holiday period of July - mid August. Expect to pay a minimum of about £600 at any time, although you could be looking at fares of over £1000 during peak season, so it's a pretty good idea to keep at least a bit of money saved up for any unexpected trips home.
As you will be studying, you are eligible for special student priced flights. STA Travel have branches in both Australia and New Zealand as well, so it may be worth getting an ISIC Card (International Student Identity Card) to access these discounts, as well as getting money off other activities.
Hunt through the deals when you're travelling, and start early! Although travelling on a student visa means that you shouldn't be expected to show a pre-booked return ticket, you may find that the big airlines will sometimes offer better deals on return tickets.
Flight comparison sites are a good way of keeping up-to-date with current offers by the airlines, but you can also check their websites directly for updates and specials. Some of the main airlines flying to Australia and New Zealand from the UK are: