While I hadn't been able to join an occupation on a Sunday, I went to my local occupation this afternoon and spent an hour or so there drinking tea and putting the world to right. What follows is not an in-depth access survey, but is rather the impression I got, based on the information I was told or observed.
The Sheffield Occupation is in front of the Cathedral, so trams and buses stop nearby. It is on a flat courtyard and while there are some steps to access it from some directions, there are sloped alternatives alongside them.
The Occupy Sheffield has one portaloo, which is not accessible. The local Quaker Meeting House is offering the occupiers use of their toilets, and they do have wheelchair accessible toilets on each floor (with lift access to each floor). Once they close from 9pm - 9am, use of the portaloo begins, excluding many disabled people from using it.
The closest Changing Places toilets to the site are at Sheffield Town Hall and at Ponds Forge Sports Centre.
They have generators for electricity, but try to only use these at night. They also have gas heat, which is basic. If you need electrical power for any of your equipment, this could be problematic at the Occupy Sheffield camp. If you have a need to keep warm that would go beyond wrapping up really well, then again it may be an inaccessible protest for you in that respect too.
There is a good supply of food and hot drinks. I was the only visibly disabled person at the camp when I was there, but talked to a man who was a mental health service user. Another disabled person had clearly been at the camp at some point too. This photo is of a piece of paper taped to the main tent, which reads "I am one of the few disabled people who has a job. I am mad about what our society has become. I am the 99%".
The photo at the top of the post is of the main tent. It has a large banner on it, reading "Occupy Sheffield", and another fabric banner reading We Heart NHS. It was taken by me.