Ben We've had similar problems, notably with some of Willie's data where he applied a correction that encompassed both compass error and declination. The result suggested was to insert a line
declination 0 degree which zero's the declination correction. One can then add a line such as calibrate compass +11.5 in our circumstances, not needed in yours where the alignment with grid north has already been made. As far as UFS is concerned, it's also worth noting that Therion recognises the local grid so you can use cs: OSGB:ST Graham
