With acknowledgements to Eurocontrol:
"Mode S Enhanced Surveillance is planned for deployment in France, Germany and the United Kingdom. The foreseen mandate is March 2005, with a transition period until March 2007.
Enhanced Surveillance through the ground acquisition of specific aircraft parameters will enable the Controllers to increase their efficiency in tactically separating aircraft. The Controller's information is improved by providing actual aircraft derived data such as Magnetic Heading, Air Speed, Selected Altitude and Vertical Rate enabling to reduce the radio telephony (RT) workload "
My italics
24 bit code instead of just 4096 code options is used. As BJJ says - it is coming!