Ok I bit the bullet and held on the phone to immi for 25minutes and found out that no one keeps track of the work time its up to us and it's our fault if we go over it.

If we want to work longer we have to apply for a Work Visa. Which you need a letter from your employer blah blah blah...

They werent much more help than that. I asked what would happen if I went over the 12 months by accident and she said that would be my fault (laughed on the phone to me) and said I should keep a better count of how many months I've worked for.

Note to all WHV peeps - keep track of your time spent working just in case!