Sainsbury’s partners with etiquette experts Debrett’s for a guide to Christmas gift-giving   Debrett's new guide to festive faux pas says a text message thank you isn't enough; don't Insta-boast and always bring a bottle for the host - but don't expect to drink it yourself. London, 2017-Dec-01 — /EPR Retail News/ — Sainsbury’s has teamed up with etiquette…