The Damixa 62000 series taps use a CD insert 13297/13298.
You might get original inserts.
However the '8mm' B& Q own brand inserts are 20 spline , which is correct. They just push the tap-turning-on bit out by 1mm - does not matter, and they work fine. I think £16 for the pair. Bargain !
Bodger
October 2011