ICAO license transfer to UK CAA

[Zonkor]

I have an EASA PPL issued by the UK CAA. Recently I obtained a national (but ICAO-conform) soaring license from another European country. This country has not fully switched to EASA yet, but it is already possible in that country to convert the national license to an EASA SPL or LAPL.

Sooner or later I'll have to merge my EASA licenses. (You can only have one EASA State of License Issue.) So my question is:

1. Can I directly transfer my national license to the UK CAA?

-OR-

2. Or will I have to first convert the ICAO soaring license into an EASA SPL in that country, to then transfer it to the UK CAA?

I enquired with the aviation authorities in both countries with not much luck so far.

Any info on how to accomplish this and procedures would be appreciated. Thanks!