Chewy... In the UK aircraft types are categorised for wake vortex purposes and ATC will provide the requisite separation.
On first contact with most UK ATC units pilots are required to state their aircraft type to confirm the flight plan information held by ATC. For this reason it is not mandatory to keep saying "heavy" as the controller is well aware of the type of aircraft he is dealing with. Requiring pilots to state the type of aircraft is because airlines are renowned for changing aircraft at a late stage and not informing ATC!