Hi Caz
You can contact the DWP and tell them that you wish to put in for a change of circumstances because your condition has worsened. Keep a note of the date that you inform them. This will trigger a review and they will send you out a form and you fill it in with additional evidence that you have. You are likely to be subject to a telephone assessment. ( a few people are being called for face to face).
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
