You Do Need power plug adapter while traveling from Belize to Isle of Man.

Here is Why You Need An Adapter

The outlet and plug type used in Isle of Man are C and G and in Belize are A, B and G. This is how they look like.

Belize

In Belize, outlets of type A, B and G are in use.

Type A

Type B

Type G

Isle of Man

In Isle of Man, outlets of type C and G are in use.

Type C

Type G