This is recommended Gondukin,
1. Add SSEA to your NPPL(A)
OSF are fine for this; there are plenty of others.
2. Convert your NPPL(A) with SLMG & SSEA to a LAPL(A) with TMG & SEP
Paperwork & cash only
3. Upgrade* your LAPL(A) TMG & SEP to PPL(A) TMG & SEP
This is where the minimum of 15 hrs aeroplanes comes in
Google: 'FCL.210.A PPL(A) - Experience requirements and crediting'
* I would call it a downgrade
4. Within that reference, you will also find an alternative route from LAPL(S) to PPL(A) via TMG flying.
Enjoy