The relevant sections of Art 163.
Medical requirements for specified United Kingdom licences and National Private Pilot’s Licences are:
(3) The holder of a licence makes a medical declaration in accordance with this article if they—
(a) reasonably believe that they—
(i) meet the medical requirements for a Group 1 Licence issued by the Driver and Vehicle Licensing Agency; and
(ii) are not subject to a disqualifying medical condition.
(6) For the purposes of this article, “disqualifying medical condition” means any physical or mental condition or illness, or any history of such a condition or illness, including—
(a) any alcohol or drug abuse, addiction or misuse;
(b) any neurological condition;
(c) any functional disability;
(d) any surgery or medical treatment;
(e) any collapse, fainting or loss of consciousness;
(f) any history of (a) to (e); or
(g) such other medical conditions as the CAA may specify,
that might impair the safe operation of normal flight controls or render the licence holder unfit at any time to perform any function for which the licence is granted.
A LAPL medical certificate seems a lot simpler, particularly now that the recent amendment to Part-MED states:
MED.B.005 General medical requirements
Applicants for a medical certificate shall be free from any:
(a) abnormality, congenital or acquired;
(b) active, latent, acute or chronic disease or disability;
(c) wound, injury or sequelae from operation;
(d) effect or side effect of any prescribed or non-prescribed therapeutic, diagnostic or preventive medication taken; that would entail a degree of functional incapacity which is likely to interfere with the safe exercise of the privileges of the applicable licence(s) or could render the applicant likely to become suddenly unable to exercise the privileges of the licence(s) safely.