\TrackLangProvidesResource{GB}[2016/10/06 v1.2]

\providecommand*{\GBunits}{%
  \renewcommand*{\weightunit}{kg}%
  \renewcommand*{\lengthunit}{mm}%
  \renewcommand*{\currencyunit}{GBP}%
}

\TrackLangAddToCaptions\GBunits