Just sharing in case it's of interest to Three customers. I've seen occassional Dunnes offers over the past 6 months. But based on the T&Cs in the current Dunnes 3Plus offer, it looks like it will be an ongoing thing as it says "vouchers limited to 1 voucher per 3Plus user per month"

https://plus.three.ie/offers/shopping/5851/10-off-40-shop-save-grocery-voucher