Central Heating System?

I've just bought a house that only has electric storage heaters working off an economy 7 supply. Hot water is from immersion heaters in the hot water tank.

I would like to perhaps install a different system that will be more cost effective, and am wondering what the best options might be in the UK.

The house is a 1940's semi-detached in Glasgow (so solar power might not work, though rain power might!!), has a main fireplace downstairs and one up stairs that can be opened up (good condition, just need the metal work and wood to burn), large front and back garden. Nearest gas supply is 200m away so will cost a few thousand to install gas main plus a few thousand to install gas appliances. The house has cavity wall insulation and double glazing, loft insulation is about 100m deep (haven't had chance to check yet) and can put additional insulation in there (I want to board out the loft, insulation can also go under the tiles). I have no idea about underfloor insulation - probably none. Instant heat will have to be from electric fan heaters.

So there it is. What are the best options for me - I want to make the house warmer, have hot water and cost less over the next 5 years or so.

If you can give me an estimate of cost and potential savings that would be even better.

The answer might be to leave it as it is and have higher electricity bills but not spend thousands to reduce the power costs