I knew someone (or several people) would say Vienetta. That was my first thought before I opened the thread. I still think of it as being posh, despite the fact that it's really cheap and available in Iceland now!
Imperial Leather soap - we occasionally had it if it was on special offer, but mostly we made do with the Co-op's own brand. I always buy Imperial Leather soap now!
As a teenager I remember reading the Sunday Times supplements and there were always references to people eating sun-dried tomatoes which I assumed were really posh.