I am currently looking to go travelling in 2005 but am very interested in doing a PhD in Sept. 2006, is it possible to apply now and defer entry to a PhD or should I leave it and apply next year?

You can try applying early, but funded projects need to be started at set times. If there is a very specific area of research that you are interested in it may be worth writing to the relevant academics to stake your interest in a 2006 place, but they will not know if they have anything available or not as the funding decisions will not be announced for some time.

I took a year out to travel and waited to apply till January this year to start September this year. It has all worked out really well, and my travels impressed the interview panel. I've ended up with a fantastic PhD project compared with those available last year!!