Ladies & Gentlemen,
Many thanks to all who responded and gave excellent advice.
As a result I have now resolved my problem and can successfully continue by build.
Along the way I came across a German Tap Die Seller of New / Used Taps & Dies of All Sizes - having 3,000 plus in stock. If you are interested you can find them on Ebay at
https://www.ebay.co.uk/usr/www-mobileme24-de
Kind regards and wishing you all to keep safe,
Andrew