All in good spirit, Pete!
Robin - yes I remember them well, although my cadet days were a little earlier, 1958-63.
.303 drill rounds make a great collection on their own, as there were so many different types approved. I think I list 38 official variations in my .303 book, including Local Pattern and expedient types, but excluding different finishes and other minor differences.
In my collection I think I have about 130 different .303 inch drill and dummy rounds, but then I do not bother with every tiny variation or different date.
The drill rounds you remember from Cadet days were the Drill D Mark 10, which was introduced in 1950 to effectively sweep away all the older and expedient types that had been used during WW2. It was essentially an update of the pre-war D Mark VI but using a plated brass case instead of the expensive cupro-nickel case of the D.VI.
Picture shows a variety of different finishes on D.10s.