Try the osg_parse() function in the rnrfa package.
The RNRFA package allows convenient conversion between UK grid reference and more standard coordinate systems. The function “osg_parse()”, for example, converts the string to easting and northing in the BNG coordinate system (EPSG code: 27700), as in the example below:
# Where is the first catchment located?
someStationsThe RNRFA package allows convenient conversion between UK grid reference and more standard coordinate systems. The function “osg_parse()”, for example, converts the string to easting and northing in the BNG coordinate system (EPSG code: 27700), as in the example below:
# Convert OS Grid reference to BNG
osg_parse("SN853872")
https://cran.r-project.org/web/packages/rnrfa/vignettes/rnrfa-vignette.html
Also see: Converting (British) National Grid references | R-bloggers