I hope that Galway Hooker being listed as a lager is a simple error. Otherwise the Porterhouse have overstepped the mark.
It is up to the manufacturer to position and market their product as they see fit. If Hooker Brewery sell their beer as an Irish Pale Ale, the Porterhouse, as a retailer, have no right to reclassify it as a lager, regardless of how sales might be affected by the change in classification.