Does this seem right? I could put it all through the Myson to
completely cross-check it but it's a lot of extra work ...

Victorian terraces are actually quite good on energy conservation, despite
the lack of insulation and cavities and old leaky windows. This is because
the "external" walls are primarily party walls, with only thin slivers of
genuine cold outside walls at the front and back. The worst parts are the
rear extensions.

The survey SAP rating on mine when I moved was good, despite no insulation
(other than the roof) and single glazed sashes at the back. It is a 3
bedroom Edwardian (Victorian style) mid terrace.

I calculated my losses to be around 8.4kW, but this is probably higher than
most would calculate, as I calculated the lounge and dining room at 22C and
bedrooms at 20C. This is for an outside temperature of -3C.

Christian.

P.S. Have you finished that bathroom yet, John? The old Glowworm Fuelsaver
has started making a funny noise.