UK police aircaft are invariably very heavy, with an empty weight in the lower seventies as a percentage of the maximum weight. This will typically allow a three person crew and around 2 1/2 hours endurance to dry tanks [it varies a bit if you have, say, the older, lighter version of the EC135]. Take out a 30-minute reserve and there should be the capability of flying for 1 1/2 hours with either a fourth person or the option of topping up to two hours. MG's figure does seem a little low, perhaps with an extra seat fitted and an unusually heavy crew.