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

Here is Why You Need An Adapter

The outlet and plug type used in Sri Lanka is G and in Isle of Man are C and G. This is how they look like.

Isle of Man

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

Type C

Type G

Sri Lanka

In Sri Lanka, outlets of type G are in use.

Type G