A friend of mine is running an outside bar business but is unsure over the measures of spirits and liqueurs, he knows that spirits in general are sold in 25mls (some pubs have 35mls) but what size should port, sherry and liqueurs be sold in and what defines the size, he has asked trading standards but they were less than helpful, is there a website that explains what the rules are?
Thanks for your answers so far, but what I was trying to get at is spirits such as gin, whisky, rum etc are sold as 25ml but at what alcohol point does a drink become classed as a spirit? for example Tia Maria is only 20% proof so it is normally sold in 50ml shots so when is a drink officially classed as a spirit?