During our mix down process of the sound for George we adhered to the technical standards for delivery of television programmes to BBC. This meant following the guide shown below:
This is also available on page 13 of the document here: http://www.bbc.co.uk/guidelines/dq/pdf/tv/TechnicalDeliveryStandardsBBCv3.pdf
We did this as we wanted to work to a professional standard, and in the industry itself these are the guidelines we would have to follow normally.