Disability Rights UK have just completed a report on the PIP process, which is free to read/download here (just follow the links):
The report was compiled from interviews with over 1700 people with disabilities and long term conditions, including lupus and other auto-immune disorders.
As you might imagine, there are some pretty damning testimonies in it; some of them echo very closely the experiences of people here who have written in this group about their difficulties with the process. DRUK are also running an online campaign which invites people to contact their MP about the problems with PIP.
So don't forget to do your calming meditations after reading the report, then write to your MP here