when to start looking for a new job

[Frizz1986]

I left my current job for maternity leave at the end of 2013 and am planning on taking a full year off.
If i return to my job i can also take 33 days paid holiday at the start if 2015 so wouldn't actually step foot in the office until mid feb even though i would be getting paid full wage from jan.

Anyway i really don't want to return to my job. I didn't particularly like it when i left but i got on with the team i worked with. Well lots of them have left now so there is just the job left and i wont be the same person anymore.

I fancy looking for a new job but want to keep things open in case i don't get anything and need to go back.
When should i start looking as i don't know when i would need to tell my employer that i will be coming back.
Also if i could hold off starting a new job until mid feb that would be fab but is that going to cause issues if i tell my employer that i am returning in feb (using my holidays from jan) and then i start looking for a new job in jan (with an aim to start it in feb)
Its all so confusing!