So decided to fit the the new markers. Old ones removed easily and needed to widen the holes to the 6.5 of the marker. So used a standard 6.5mm drill bit and widened. The holes in the fretboard were pretty deep and needed to be filled. So the only thing at hand was some paper towel and tamped down a bit at a time and lightly soaked in superglue and gradually built up to the required level. Glued in the new markers and then filed down to level before sanding back.
A little more fine sanding to finish and then can start the fretwork.