You Do Need power plug adapter while traveling from Greenland to United Kingdom (UK).

Here is Why You Need An Adapter

The outlet and plug type used in United Kingdom (UK) is G and in Greenland are C, E, F and K. This is how they look like.

Greenland

In Greenland, outlets of type C, E, F and K are in use.

Type C

Type E

Type F

Type K

United Kingdom (UK)

In United Kingdom (UK), outlets of type G are in use.

Type G