You Do Need power plug adapter while traveling from Great Britain to Cuba.

Here is Why You Need An Adapter

The outlet and plug type used in Cuba are A, B, C and L and in Great Britain is G. This is how they look like.

Great Britain

In Great Britain, outlets of type G are in use.

Type G

Cuba

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

Type A

Type B

Type C

Type L