David Hardwick was right to qualify Bernard's concerns about errors in covering modern mining history. From my experience, the more recent one comes, the harder it often is to get decent data. Many companies seem to have been wholly owned subsidiaries of larger ones - so detailed annual reports are not published. Very few of them have been covered in the mining press - presumably because they are/were mostly insignificant. Government statistics revert to being almost of no value for 'miscellaneous' mines from 1951 and for coal mines from around 1993.
I've been lucky in having access to one or two old 'spar' men, who've helped me with information of small ventures which would otherwise have left little trace. Even so, their memories are not always perfect when it comes to specific details. David is right to say "Write it all down Bernard - your knowledge is important for future generations" - and the current one too.