If mains gas is too expensive you could always consider LPG (propane).It means getting a tank installed but a lot of companies do not even charge for this as long as you do the civil works.You will have to buy an LPG compatible boiler and the gas is always more expensive,but you could be up and running for a few hundred pounds,compared to the potential costs of getting mains to your door.I have known TRANSCO charge �12000 to take it across a main road.Also there can be a long wait before they can do the work..Good luck.