Hi Barbara
I have moved your post. We ask people not to ask questions on another person's post or it may lead someone to get the wrong answer.
I don't think it is a deliberate ploy on the part of the DWP. I think you have been sent out a standard letter that a lot of people are receiving. You may still find that you hear from them separately about your 'change of circumstances' ie - you worsening mobility.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
