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

Here is Why You Need An Adapter

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

Andorra

In Andorra, outlets of type C and F are in use.

Type C

Type F

Northern Ireland

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

Type G