You definitely need to book early, as soon as they are released if poss, then you get the chance of a bargain.
Depends which airline of course, but I am in Tenerife from Jan to March 2013 - I usually fly either Monarch or easyjet but chose Easyjet this time as they were cheaper.

The winter 2012/13 flights were phased in gradually, releasing a month at a time, so I had to book my Jan flight out in March this year, but as they hadnt yet released the March 2013 flights then for my return home I booked it as a one way.
Then in April 2012 Easyjet released their March 2013 dates so I could book the flight home, unfortunately doing it this way incurred 2X £9 booking fees instead of one but if I had waited until April to book a straight return instead then the outward flight would have already shot up in price from original release date.
Its a delicate balance to get it right!

I would suggest that from mid Feb onwards next year to start checking the airlines' websites for their winter flights on a very regular basis as they often release flight dates without any fanfare.
Also ask to be put on their emailing lists although that is not foolproof.
Just noticed you are from Chadderton so you will be flying from Manchester, which is where I fly from so all my info should be relevant for you

Thanks Vivien-Marie
Most helpful, and much appreciated.