Thankyou for your replies - I will pass on and if required may ask for the details you have Mr Angry. Not aware that my colleagues associates are experiencing the same issue but would be fairly certain or it would be victimisation at the very least. Will ask and advise accordingly.
Interpretation for me of CAP 371 is that SBY duties are maximum 12 hours and pre notified on roster of hours start and finish ? this does not take in to account being called from SBY to carry out a duty and FDP calculation.