Just incase any one is looking for more information.
As stated above both classes expire at different times, (until its synched up), if your M2 renewal is up (like mine is) you can either redo the m1 test and get your m1,redo the m2 test and effectively renew your m2 (I don't really know why you would do this. May as well book your M) or take the m test and get your M. I thought the m2 was good for just a normal renewal until i got a letter from the ministry.