Here are links to the UK CAA's information pages which outline the medical certification proceedures for:
EASA Light Aircraft Private Pilot's License (LAPL), EASA Private Pilot's License (PPL) and EASA Commercial Pilot's Licenses
CAA Medical Algorithms.
If you have a medical condition and are not sure of the procedures you may be required to follow, here is a link to the CAA's information page to guide you. If flow diagrams and medical terminology are not your thing, please call and and I will be very happy to help you.