Hi,
Under the EASA Licence transition reports in CAP804 you can convert your NPPL SLMG directly to a full ICAO PPL licence with TMG restriction, and then remove the TMG restriction once you have the licence by some SEP training and skills test.
Choose from one of two obvious conversion routes:
(a) Non-ICAO 'LAPL(A) with TMG Restriction' (CAP 804 pages 494 & 495)
OR
(b) Full-ICAO 'PPL(A) TMG Only' (CAP 804 Pages 502 & 503)
You will need a Class 2 medical for the PPL or a LAPL medical for the LAPL.
Check the requirements in CAP804.
Would be the easiest route to a full ICAO PPL licence.