Just looking at one of mine, it's a D. Next door (identical) is a C.
Mine (D - 66):
Feature Description Rating
Wall Cavity wall, as built, no insulation (assumed) Poor
Roof Pitched, 100 mm loft insulation Average
Roof Flat, limited insulation (assumed) Very poor
Window Fully double glazed Average
Main heating Boiler and radiators, mains gas Good
Main heating control Programmer, room thermostat and TRVs Good
Hot water From main system Good
Lighting Low energy lighting in 67% of fixed outlets Good
Floor Suspended, no insulation (assumed) N/A
Secondary heating None N/A
Next Door (C - 69):
Feature Description Rating
Wall Cavity wall, as built, no insulation (assumed) Poor
Roof Pitched, 100 mm loft insulation Average
Roof Flat, no insulation (assumed) Very poor
Window Fully double glazed Average
Main heating Boiler and radiators, mains gas Good
Main heating control Programmer, room thermostat and TRVs Good
Hot water From main system Good
Lighting Low energy lighting in 89% of fixed outlets Very good
Floor Solid, no insulation (assumed) N/A
Secondary heating None N/A
So I just need to get a few more low energy bulbs? The flat roof (assumed) very poor i'd contest as I know it's full of insulation between the rafters having replaced the roof in the last few years.