I don't post here very often - I just pop in when I've seen something that might be useful to you.
I'm posting a link to the DWP's revised assessment criteria, which have been changed quite a bit due to issues that were raised during the first consultation period.
I'm afraid it's quite a lengthy document, but you can probably go through it and read the bits that are applicable to your situation.
Hope this is of help to someone.
www.dwp.gov.uk/docs/pip-second-draft-assessment-criteria-note.pdf