If you are looking for the cheapest, go to this site
http://www.justtheflight.co.uk/scheduled-fligh ts/destinations.html
and enter your details. You will probably find BA and Virgin come up cheapest. This site will give you a guide price. Then visit the sites for the actual airlines and see what prices they give. I am flying to Sydney in April. As this was for aholiday planned in advance, last year I kept putting my details into Virgin and BA to see when the price would cheapest if I was flying last year (if you see what I mean). Virgins price was cheapest around February and BA's in March, but of course all the bookings may be gone by then. I noticed in the paper last October that BA were doing a sale and I got about �500 off the World Traveller Plus rate, which has still not been bettered by either Virgin or BA. I'm afraid its a case of looking and seeing how long you are prepared to wait to book. One of friends who is a travel agent never books her flights more than a week ahead, but I like to know I've got a seat on the plane!!