We had our first sessions on this last Wednesday - we just had an open exploration of "accessibility" and how it may relate to the consultation.
One of the issues that became clear for the next stages is the importance of stories (narrative) and how these can provide insights to accessibility issues. They can allow you to explore the problems and issues much more deeply than if you concentrated on technical or architectural solutions.
There can be a tendency to converge on solution or actions to early so hopefully as this design process builds it will shed new and possibly unexpected light on the issue.
(i did say I was going to use the original post for updates but I can't seem to embed images in the comments....)