On Track
NATS have produced a very good training DVD which explains exactly what they mean by the errors. It is available to order on line and is free, the copyright also allows you to copy and distribute as much as you like.
It is well worth viewing as it contains some excelent advice and infomation for both experienced and inexperienced crews alike. I believe all transatlantic flight departments should issue a copy to each crew member.
Unfotunately I am down route for a while and do not have the link available but I am sure someone will be good enough to post it here.