My understanding was that if all valid ratings went across at the same time when converting from UKPPL to EASA PPL, you would only pay for the licence issue fee. If you added ratings one at a time, then yes it would be an expensive exercise.
You may be right, but for glider pilots and tug pilots the towing and aerobatic ratings are new, as is the actual SPL (sailplane licence) or LAPL(S). If it goes ahead the SCFR (sailplane cloud flying rating) will also be new so no choice but to add them individually.
Whatever happens to the IMC rating may have to be done individually if done after initial EASA licence is issued. The CAA will have very shiny windows (see earlier post).