Hi looneytunes,
You will undergo very little, if any, physical examination during the assessment. You will certainly not be asked to remove anything more than outer clothing. If you are asked to do anything that will cause you pain you can refuse - but you must make absolutely certain that the assessors understands your reason for doing so so that s/he cannot report that you simply refused to co-operate.
Our ESA guides include a section that explains what to expect from the assessment.
Nothing on this board constitutes legal advice - always consult a professional about specific problems