Set in the arctic / Antarctic with several different huts and a team of scientists. Slowly they get struck down by a mystery virus which turns them into monsters who's tongues shoot out even when their heads are cut off. This enables them to drag them across the floor. I saw this on TV about 25 years ago and would love to know what its called please.
That sounds like John Carpenter's remake of The Thing, (1982).
Scientists in the Antarctic are confronted by a shape-shifting alien that assumes the appearance of the people that it kills.
There is a scene like you describe, with a severed head pulling itself along the floor with a long prehensile tongue. You can watch that clip here.