In reply to pasbury:
Before my parents had their solar panels fitted, they had to get an EPC - was paid for out of the money paid for the panels, but cost around £60-80. The house had recently been fitted with double glazing, is fully insulated in the cavity walls and has tonnes of insulation in the roofs so we scored about as highly for a 30's home could.
The guy suggested some other measures like underfloor insulation (only half the house currently has this). That would be stupidly expensive as the floors in the other half are solid concrete. He also suggested replacing the ~20 year old boiler, which my parents can't afford, and replacing all lighting with energy saving.
Following the installation of the panels, they were given an energy monitor and my dad became obsessed with energy saving, so he has now replaced the recessed halogen (50w) downlights throughout with LEDs. This has saved a massive amount and I would highly recommend everybody does it! The light they give out is a much nicer white than the yellow a halogen does.
If you want any more information on what they got then just ask. As it happens I am currently doing a research project on renewable energy in the home, so anything you might be able to tell me as well could be useful!
Cheers