Fair point Malcolm, not half as much fun though :-)
Having looked at taking the cupboard doors of as being the "right" answer I concluded they were rather well stuck to be disturbed so took the option of a new hole in the top of the cupboard. 6mm auger bit down the bolt hole from the top for a pilot hole then there was just enough space with a hole saw on an improvised extension to cut on not too bad an angle. Not visible in normal use and easy access to the nut.