Hi Emma
Congratulations on winning your award. Unfortunately, because of the length of time you have been given an award, you need to get onto the DWP immediately to find out whether you are going to have to put in for a new claim or whether you will be sent a review form. If you don't do this, you may find that your money simply stops.
If you have a benefit claim up and running, a supersession is the legal process for changing your award if something about your circumstances has changed. In effect, a supersession says that the original decision was correct, but it now needs to be replaced (superseded) because of the new factor. You say that your condition has got better, but not significantly. However, you may find that the DWP disagrees with this, especially as your award end date is so close.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
