You Do Need power plug adapter while traveling from Cuba 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 Cuba are A, B, C and L. This is how they look like.

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L

United Kingdom (UK)

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

Type G