If this is a road going car, a heated screen is a requirement under construction and use regs if there are no heater screen vents.
Being extremely pedantic, a heated screen is not a requirement, but there is I believe a requirement for demisting IF a screen is fitted. Normally only a concern if trying to get a Caterham etc through IVA. I wouldn't have thought anyone would ever worry about it on an already registered car, its not an MOT item.
COMMISSION REGULATION (EU) No 672/2010
of 27 July 2010
concerning type-approval requirements for windscreen defrosting and demisting systems of certain motor vehicles and implementing Regulation (EC) No 661/2009 of the European Parliament and of the Council concerning type-approval requirements for the general safety of motor vehicles, their trailers and systems, components and separate technical units intended therefor
