@janic The quickest thing to do is send in a gas meter reading showing no use since February. This will raise a correct bill. Even if you turn off the gas you must still pay a daily standing charge, usually around 20p/day- £6 a month. You could switch to a new supplier with the lowest possible daily standing charge. Most people leave utilities in unoccupied properties because of the danger of freezing in winter and the convenience of having light and power and water always available. Your property will be more easily sold if it has utilities connected.