The local council should know the Building Regulations quite well - it's their job to enforce them.
There have been ammendments to the Building Regs with respect to energy conservation - this link might help...
http://britishgas.home-maintenance.info/heating/energy-regulations/
and this...
"Radiators
Any new radiator installed will require a thermostatic radiator valve (TRV) to be installed. A TRV gives better control over the individual room temperatures. It is also encouraged to place TRV's on existing radiators."
from here...
http://www.planningportal.gov.uk/england/genpub/en/1115315223646.html
So - you could buy a TRV - fit it - call the council in for an inspection - and then make a decision to leave it as it is or replace it with a regular valve.
Peccavi
June 2009