I remember when I called to get my National Insurance card changed to my married name, I was told as i was moving abroad i would need to fill in some form.
Didnt think too much of it at the time, but i read on here the same thing. Is it an actual form i need to send off or just a letter stating i will be leaving?

You can download the form from their website http://www.hmrc.gov.uk/nonresidents/fagp85.shtml

its called a P85 you dont have to send it until you have left...

Hope this helps

Kezzie