We need to buy a wedding present for a couple who live in Dublin and seeing as we don't really know their tastes, it occurred to me that they might appreciate a gift certificate from a nice store where they could purchase what they want. If looked online but can't decide if which one would be the best - if any. Has anyone any experience of shopping for household things in Dublin?

Arnott's or Clerys are both big department stores.

There are also 4 branches of Debenhams

Perhaps you should check if they have a wedding list with either of them.

Arnott's http://www.buy4now.ie/arnotts/

Clerys http://www.clerys.com/