Central Heating – how would you go about installing it in your home?

Hi. I am just about to make an offer on a house – but it does not have central heating! If my offer is accepted, I’m sure to install some sort of heating to it – radiators & underfloor heating for the bathroom. The house hasn’t been touched for many many years it seems, and I have a chance of really doing things anew, installing efficient up-to-date systems.
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But I am completely baffled as to how go about this. Should I choose oil/ gas/ electricity… for example? How much does everything cost to do up?? (it’s a semi-detatched 3 bed house by the way, if this info helps) And who / which establishment should I ask to do it for me??? I hear british gas is expensive…
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Any suggestions, comments appreciated. Thanks.