According to press releases about 'Residence' class Butlers will be trained at the famous Butler training establishment in London. Probably this one -
British Butler Institute
How they bring their skills to an aircraft who knows. However I can't imagine a Butler wafting around with one hand behind his back carrying a decanter of port on a tray in the other. Hope they pass their SEP course though.
Whose going to be the first to ask for an upgrade :-p