Possible Clues:

• They're perfect for an evening out with bubbles and the barman will be aware of them if he's done a stocktake?
• They're perfect for those looking for an evening out and the barman will be aware of them if he's done a stocktake?
• They have a way of setting things straight in The House by determining the number of Shadow members presumably?
• Without them The House would be all over the place in the bar, and to be frank, that's some introduction
• They keep the House straight initially with whiskey and a number of stories
• They keep the House straight, initially, with whiskey measures
• Flat-finding agencies