As far as I know, postal charges in the UK are always metric only. One reference says that the UK Royal Mail went metric on 29 September 1975
http://www.gbstamps.com/gbcc/gbcc_rates1.html
As far as I know, postal charges in the UK are always metric only. One reference says that the UK Royal Mail went metric on 29 September 1975
http://www.gbstamps.com/gbcc/gbcc_rates1.html