Fuselage length: 19.5 meters : 64 feet.
Length (with rotor): 22.8 meters : 74 feet 9 inches
Height (with rotor): 6.65 meters : 21 feet 10 inches
Main rotor diameter: 18.6 meters : 61 feet
Empty weight: 10,500 kilograms : 23,150 pounds
They're from memory, as you can see it's quite heavy so don't just look at dimentions, however, the Merlin can be landed just about anywhere anyway. The mountain rescue with have much more equipment on board that would add extra weight.
I feel you best bet would be to contact them and get specifications off them, aswell as speaking to the experts.