To clear things up:
There is NO 'duty free' allowance for ANY travel within the EU (irrespective of the countries which you're travelling between) . You can only make genuine duty free purchases (subject to strict limits) when travelling into, or out of, the EU.
The cheaper fags booze you can buy within some other EU countries - either in local shops or at the airport -are 'duty paid', not 'duty free'. (i.e.duty has been paid at local rates). You're entitled to bring back a theoretically unlimited quantity of such purchases, as long as they're for your personal use (which includes
bona fide gifts to others, for which you'll receive nothing in return, but not goods for which you'll receive payment - even if you don't make a profit). However HMRC have 'advisory limits', beyond which they will challenge travellers about whether their imports are genuinely for personal use. Those 'advisory limits' are here:
http://www.hmrc.gov.u...riving/arrivingeu.htm
However the 'duty paid' prices of ciggies and booze in the Irish Republic are generally slightly above those of the UK, so travellers to Ireland are unlikely to make any savings by buying them there.
Chris