Exemptions from the requirement to pass the TMG Skill Test apply for current UK PPL (SLMG) holders with a defined level of experience. They are clearly stated in LASORS.
Such exemptions do not apply to JAR-FCL PPL holders with SEP Class Ratings.
There is no 'TMG license' (sic) per se - the TMG Class Rating may be included in any JAR-FCL pilot licence.