I would suggest that Budweiser and Carlsberg are not "premium beers". They may be marketed and advertised as such, but there are many superior products to be sampled.
Look for Warsteiner in Tesco or Dunnes. It's said to be the biggest selling beer in Germany. I got 24*33cl bottles for 24 euro or less recently. I think it's lovely, and many of my friends agree.
If you like wheat beers, then Tesco have 1 euro off a 4-pack of 33cl bottles of Hoegaarden, down to 6.99. Another superb beer.
Otherwise, you can't go wrong with Erdinger, though it's not cheap.
There are loads of special offers on 33cl bottles in most supermarkets, e.g. Stella Artois, Rolling Rock, Holsten, Miller, etc. Most are about 1 euro a bottle.