When working in the offy, one of the beers I consistently used to show macro-piss drinkers there's life outside of Bud was Harviestoun Schiehallion. It's a wonderfully crisp lager made by one of Scotland's better brewers - loads of flavour, but nothing too 'out there' for first-timers.
It's in 500ml bottles and is fairly widely available (I've even seen it in Dunnes) - should come in around the 2.50/2.75 mark per bottle.