Having seen a doctor at Atos' Croydon Assessment centre who made some interesting medical statements about my abilities, I decided to complain about her assessment of me.
First, I made a complaint to Atos - by emailing their customer relations email address. Details of their Customer Charter and the email address are here http://www.atoshealthcare.com/claimants/our_customer_charter
It's only been three weeks since making the complaint, so I don't expect to have heard anything back yet. I'll give them a month and then I'll email to ask how the complaint is progressing.
I'm also contacting the General Medical Council to complain. Their complaints procedure is outlined here: http://www.gmc-uk.org/concerns/making_a_complaint/a_patients_guide.asp
I've not been able to get through to the online complaints form, so I'm printing out their paper form, and rather than handwrite the whole thing, I'll type it up and add the typed pages to the form.