Yeah, I'd believe the St Peter's website - I think the buyorganics website has probably cut-and-pasted the wrong description. I know St Peter's use English hops for most of their beers, but getting organic hops is pretty tricky over here, as there are fewer and fewer hop fields left. I imagine it's cheaper for them to import their hops from New Zealand than to try growing Hallertau organically themselves (especially as I'm not sure whether Hallertau would grow well in our climate anyway).
Having looked at the Wiki, it sounds like the New Zealand Hallertauer is the hop they use, as it matches up with the tasting notes for the beer: "a clean dual-purpose lager hop with a floral and lime zest character".
http://www.homebrewtalk.com/wiki/index.php/New_Zealand_Hallertauer
So I'd guess they use pale malt, maybe some crystal, and a single variety of hop to make this.