did you try and switch the X and the Y coordinates and see if that fixes the location?
You said originally that the GPS was set to use UTM/UPS. Try setting the coordinate system of your XY data to WGS 1984 UTM zone 30N (north). UTM 30N coords near York are the same values that you would get in France using the WGS 1984 Web Mercator (Aux Sphere) coordinate system.
This assumes that the coordinate values are around easting/x = 625000 m, northing/y = 5980000 m. (York Museum Gardens)
If not, can you post a row from your spread sheet? Or copy a row or two, export it to text/csv and post that, if possible.