LONDON, Oct 18 (Reuters) - Dutch and British wholesale gas fell on Tuesday as low demand due to warmer-than-usual weather and ample supply due to the steady arrival of liquefied natural gas (LNG) tankers put pressure on prices.The benchmark front-month Dutch contract dropped for the fifth consecutive trading day and was down 13.50 euros at 116.50 euros per megawatt hour (MWh) by 0858 GMT, the lowest level since mid-June.The British day-ahead contract fell by 23.00 pence to 35.00 pence per therm"Weak demand and comfortable supply continue to exert strong downward pressure. New weather forecasts pointing to warmer temperatures provide additional...