WD
Just address it to the DWP office that is dealing with your claim.
I just want to add that it is perfectly possible to do Permitted Work under ESA, and for it to have no effect on your claim, but it is important to remember that under IB you were evaluated by tests a,b, and c which quite likely showed no conflict. Under ESA you are being tested using a different set of descriptors, x,y and z, there still may be no conflict, but you owe it to yourself to consider this possibility.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems