You Do Need power plug adapter while traveling from Mauritius to Northern Ireland.

Here is Why You Need An Adapter

The outlet and plug type used in Northern Ireland is G and in Mauritius are C and G. This is how they look like.

Mauritius

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

Type C

Type G

Northern Ireland

In Northern Ireland, outlets of type G are in use.

Type G