Thanks to all who replied to my post and especially to David Standing 1 for the link which gives all the info one is ever likely to need for hobby purposes.
While searching for my original post I learned two things 1) that the search engine is very specific and won't pick up e.g drill under drills
2) That there are numerous postings on the same topic under different headings e.g spotting drills, spot drills, centre drills.
The late and great John Stevenson's posting on spotting drills is a concise summary of the situation
And for my next purchase……….
Chas