Normally you would consult with the disabled person to understand what the issue is and then go on to make reasonable adjustments to the work environment.

I trust that this is not your first such audit and you are attempting to fly solo! These can be very complex and the detailed interpretation of the BR documents really does need competent experienced surveyor input and there are requirements in both Part L and M as well as those spread about in other standards. The general requirements under the Equality Act can also be problematic as the general standard to achieve is to ensure that things are not significantly more difficult for the disabled than the able. Many parameters come into this and this is where you need to have experienced assisting in such audits for some time before you are competent to act as a lead auditor.