You can send it in now, but there is no hurry, and it is better to wait a bit so that you can get your PS in the best possible shape and be really certain that you have made 5 sensible choices. Most people apply in November/December.
As long as you apply before the mid-January UCAS deadline then you are guaranteed 'equal consideration; this means that all applications stand exactly the same chance of an offer whenever they were submitted. Unis do not make all their offers early on and 'run out' by November. So, dont panic and submit a weak application when actually waiting until November might have meant your application was in better shape and you might have actually got an offer. You only get one chance at this - make sure its the best application possible.