Thanks for the reply girls.

I've done some ringing around after my meeting with my employer (who I ended up telling that I will give him a letter later in the week). I found out that I can say that I am going to have less than the 12 months off from a certain date and if I want to change it later on I just need to give 4 weeks written notice. If however I say I will take the full 12 months now my employer does not have to let me come back earlier if I want to, it is totally up to them. So to cover my butt (financially anyway) I am going to tell them I will take 7 months and return to my current hours and role after that. At least then dh and I have gave got plenty of time to improve our finances and hopefully I will be able to take the full 12 months or not go back at all I also need to specify what hours I will be returning to and anything different to what I put in that letter is up to them to agree on. So again to cover my own butt I will just say that I will return to what I do now and i can always then change my mind and work less if that is going to suit better. I know they will have staff to cover my hours if that ends up happening so I don't think I'd be doing the wrong thing by them, instead I am just making sure I have a job to go back to if I need it

Thanks again