Thanks for the suggestion Laurent, however the slot between the head and the column is just under 12 mm and even if the recess on the head is enlarged there isn't enough room for the leadscrew and nut. I'm leaning towards a modification of option 2 with the leadscrew (ballscrew) fixed to the top of the head between the motor and column and a rotating ballnut mounted high up so that it clears the motor in the up position of the head.

Russell.