Hi tb555,
I am a little unsure of the circumstances relating to your question. Were you hoping that you would get into one of the ESA groups* without a face-to-face assessment, or had you asked for a home visit? Either way, you should not assume that your GP has not backed up your claims as this is entirely at the discretion of ATOS. I am afraid that you have little choice other to attend the assessment** otherwise you run the risk of your claim being closed and your file returned to DWP.
* I assume you are talking about ESA as you mention a 'back to work' assessment.
** Unless you are, medically, totally unable to do so. In which case, please come back to this thread and tell us.
If I have read this totally wrongly and you are talking about something different, please come back and explain your situation.
Nothing on this board constitutes legal advice - always consult a professional about specific problems