Not to sure if this is correct one of my Facebook Friends have said this:
"A tip, when the DWP say you don’t need a Doctors cert anymore, get one away, the GP will have the same letter saying no need for a cert, the GP maybe not willing to do one, but remind them that, they signed you off before, so whats the difference! Without a GP’s cert as backup you’re open to the DWP/ATOS saying your fit for work! Remember a GP overules the DWP/ATOS. I have now refused any DWP/ATOS appointments because of this, they cannot overule a GP, the GP knows you better than anyone, so fight all the way!
Regards Debbie x