Well I didn't find one per se @funbobby51 , I booked a telehealth appointment with my regular doctor's surgery / General Practice which i've been seeing since i've lived in the local area.

They had over 3-4 years of my medical history on their patient records and although there wasn't anything in there too extreme that would exempt me immediately (such as a chronic lung condition) there was enough prior medical history for me to substantiate very easily why I required an exemption.

Put it this way: wearing a face mask is bad for your health. If you are in a state or frame of mind which a fact like that will really weigh on you, then being forced to put one on is causing harm to your health mentally (and physically).

Here is a hypothetical situation: what would a doctor do if you said you will commit suicide or stop breathing if you were forced to wear a face mask. Would they be compelled to exempt you? Would they use their better judgment and medical know-how to diagnose you with whatever it takes to preserve your life?