You Do Need power plug adapter while traveling from Wales to Saint Kitts and Nevis.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Kitts and Nevis are D and G and in Wales is G. This is how they look like.

Wales

In Wales, outlets of type G are in use.

Type G

Saint Kitts and Nevis

In Saint Kitts and Nevis, outlets of type D and G are in use.

Type D

Type G