Just remember however that Lat and Long Greenwich Derived position, is not what a GPS runs off. Most GPS run off WGS84 which is different. If you are transposing from OS to GPS check what system your GPS is set to and there are several systems, or you may find that you can be up to 3 miles out
As far as I am aware there is no GPS that runs Lat & Long GPD so beware, or take your sextant and chronometer with you
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Riding with enthusiasm upon the ragged precipice of disaster