Converting NPPL (SLMG) or LAPL (S) TMG to SEP

[gliderpilotuk]

I'm struggling to find any info on the conversion from TMG licenses to SEP and wondered if anyone could help.

I've been told there are 2 routes:

1. Convert LAPL (S) TMG to LAPL (A) TMG, then add SEP.
2. Add SSEA to NPPL (SLMG) then convert to LAPL (A) TMG with SEP. This entails diff training for the SSEA then paperwork.

Any advice on best route would be much appreciated.
Also, can this be conducted by a CRI, ie non-ab initio instructor?

Thanks,
Paul