I thought that most housing associations work to the "decent homes" standard. The detailed guidance on heating copied below - I can't see any reference to a radiator in every room. It says "two or more".
I would ask them to supply you with a copy of the regulations to which they are referring.
Source
Criterion d: It provides a reasonable degree of thermal comfort
5.23 The revised definition requires a dwelling to have both efficient heating; and effective
insulation. Efficient heating is defined as any gas or oil programmable central heating; or
l electric storage heaters; or
l warm air systems; or
l underfloor systems; or
l programmable LPG/solid fuel central heating; or
l similarly efficient heating systems which are developed in the future.
5.24 The primary heating system must have a distribution system sufficient to provide heat
to two or more rooms of the home. There may be storage heaters in two or more
rooms, or other heaters that use the same fuel in two or more rooms. Even if the
central heating system covers most of the house making a dwelling decent, under the
HHSRS a landlord must be sure that the home is warm enough for the occupant.
5.25 Heating sources which provide less energy efficient options fail the Decent Homes
standard. Programmable heating is where the timing and the temperature of the heating
can be controlled by the occupants. However this is not a requirement in supported
housing or housing for older persons where it is necessary for health and safety reasons
for landlords to ensure adequate levels of heating are maintained.
5.26 Because of the differences in efficiency between gas/oil heating systems and the other
heating systems listed, the level of insulation that is appropriate also differs:
l For dwellings with gas/oil programmable heating, cavity wall insulation (if there are
cavity walls that can be insulated effectively) or at least 50mm loft insulation (if there
is loft space) is an effective package of insulation; and
l For dwellings heated by electric storage heaters/LPG/programmable solid fuel central
heating a higher specification of insulation is required: at least 200mm of loft
insulation (if there is a loft) and cavity wall insulation (if there are cavity walls that
can be insulated effectively).
5.27 A SAP rating of less than 35 (using the 2001 SAP methodology) has been established
as a proxy for the likely presence of a Category 1 hazard from excess cold. From April
2007, local authorities will report energy efficiency using the new 2005 methodology5.
5.28 Loft insulation thickness of 50mm is a minimum designed to trigger action on the worst
housing. Where insulation is being fitted, landlords should take the opportunity to
improve the energy efficiency and install insulation to a much greater depth.
