Presumably you will convert your current UK PPL(A) to an EASA PPL(A) then from
FCL.035 Crediting of flight time and theoretical knowledge:
(b) Crediting of theoretical knowledge
(4) The holder of a pilot licence shall be credited towards the requirements for theoretical knowledge instruction and examination for a licence in another category of aircraft in accordance with Appendix 1 to this Part.
From Appendix 1 to this Part
1.2. Without prejudice to the paragraph above, for the issue of an LAPL, PPL, BPL or SPL, the holder of a licence in another category of aircraft shall receive theoretical knowledge instruction and pass theoretical knowledge examinations to the appropriate level in the following subjects:
— Principles of Flight,
— Operational Procedures,
— Flight Performance and Planning,
— Aircraft General Knowledge, Navigation.