The way the Guinness is served does I believe have a bearing on the final product, if (as often happens in England) the glass is stuck under the tap and the Guinness poured from a height until the glass is full the pint you get does not seem to be as good as when the glass is filled properly as per the Guinness method, tilt glass hold up to tap 3/4 fill glass allow the settle top up by pushing the tap away from the bar staff, allow to settle before consuming. Having drunk more than one pint of Guinness on both sides of the Irish sea, there is definitely a difference even now it is all brewed in Dublin. It may be the pressure in the barrels differ from one county to another, a rumour I had heard before today.