When is the best time to start applying for PhD's?

You should start applying for a PhD place as soon as possible. New studentships come available throughout the year and are filled throughout the year. The busiest time for PhD recruitment is from December through until March. If you want to start this October then apply as soon as possible. New spaces come available right until the middle of September (usually as a result of previously appointed candidates pulling out or not getting good enough grades), but competition is very strong if you apply this late and their are less projects available.