The more insulation the more you save. Under the new government schemes of ECO (Energy Company Obligation) and Green Deal there are a variety of ways to upgrade existing dwellings through loans that are paid back through savings from the measures you have installed.
In some case you may be able to get full funding with no payback but this will depend on your income. What ever category you fit into the options for installing energy saving measures still makes sense.
Roof and Loft
Insulating your roof space will be effective for at least 40 years and it will pay for itself over and over in that time. Most houses loose most heat through the roof.
Solid Wall Insulation
This is becoming a popular measure as if you have solid walls then insulation will reduce your energy bills by up to 40% as these let through twice as much heat as cavity walls. Solid walls can be insulated from the inside and the outside or both.
Cavity Wall Insulation
Most houses built after 1950 have cavity walls and in some cases even before this time period. Cavity wall insulation fills that gap, keeping the warmth in for longer. It can also reduce condensation inside the house, if this is a typical issue.
Insulation under floorboards can save you up to £60 per year and you can seal the gap between floors and skirting boards to reduce drafts.