Thanks Crashing Software, didn't know that had changed.
I noticed that the CAA put out another reminder as part of AIC 4/2006 (yellow 187)
"Additionally, reports from various organisations that have been monitoring Mode S utilisation (including the Eurocontrol Airborne Monitoring Project (AMP), UK CAA and NATS London Terminal Control Centre) have highlighted consistent operator anomalies in the use of Aircraft Identification (sometimes referred to as Flight Identity or Flight ID)."