The whole question pivots around your heating habits. For example, if you will only be heating to a low target temperature a room or two for a few hours and not every day at that, then in all probability in terms of expenditure alone the best choice is individual heaters (these typically cost less than £50 each) and electricity as the energy source. But if you are going to heat your entire home and constantly keep it at temperatures whereby you can walk naked from a bedroom to the shower and back afterwards without ever wanting/needing to get dressed because of it being chilly (a bit like any time between late spring and early autumn), then a complete system with a gas boiler is probably not only the system that will achieve this well but also most cheaply with any public energy supply option. If your house does not have central heating already (as it sounds like from your question) then you have system installation costs to add to the cost of the boiler, but nowadays in this country (UK) people less and less accept that indoor temperatures must plummet with the outdoor ones and thus most will attach value to a house with a proper heating and therefore you are very likely to get much of the installation costs back if/when you go to sell.