A Barbecue at Violet's - S5-E8
Continuity mistake: The BBQ fire is started by the "there'll always be an England" sign resting on the BBQ. When the guests sang that song, Hyacinth is to put the sign down behind the table where the other signs are, not on the grill.
Answer: I have asked myself the same question for a long time. It is Rosina-Queen's fine bone china, pattern "Olde England." It's the china that appears most of the time in the series. The Royal Worchester double-glazed Avignon (for candle light suppers) is really Royal Doulton Avignon, pattern "The Moselle Collection." And the Royal Doulton with the hand painted periwinkles is in reality of course Royal Doulton Colclough, pattern "Braganza."