As I sit and work today, I watch (with envy) the Islander go back and forth to Helgoland. He seems to stop for fuel every few flights, though I'm sure with full tanks, he could fly the route all day before refuelling. Obviously he would rather carry payload than more fuel than needed, for a route very well known to him.
EDXH is 480m (or 370, depending on RWY) and although the Islander has excellent STOL performance, it might play a role