TT 8n3 quiescent battery discharge on alternator main terminal is around 300mA is this excessive - baterry goes flat in 1 to 2 days if car left standing. The original alternator failed -no charge and the one fitted now is less than 2 years old.
In the meantime I have investigated further and have discovered that it is the alternator at fault, a new regulator has been fitted and the problem discharge current has been eradicated. On bench testing the alternator the repair company were reading a discharge current of 500mA so it is possible that the condition was gradually getting worse. Although the alternator regulator was definitely at fault once engine was running the alternator was still producing a healthy output, although presumably not controlled. The relatively new battery was also found to be faulty and has also been replaced (under warranty).
This question can now be considered closed.