Converting old Ordnance Survey Height Data

I’m currently putting together some pages for the Maptitude How-To pages covering Maptitude’s support for digital terrain models and elevation models. Left over from my undergraduate geology days, I happened to have the Ordnance Survey 1:50,000 height data files for the 20km SH64 square (my dissertation covered an area straddling the SH75SW and SH75SE 5km ...