Although I am American, I lived in England nearly nine years.
My family has been back in the USA for 15 years and we still miss loads of things, especially snacks.
Off the top of my head, we miss:
Quavers, Monster Munch, Polo Mints, Wine Gums, Twiglets, Prawn Crackers, Bacon-flavored crisps, Worcestershire flavored-crisps, Hula Hoops, Hob Nobs, Pepperami Sticks, Yorkie Bars, Flying Saucers, Curly Wurly's, Fruit Pastilles, Glacier Mints...
Fortunately, my MIL sends them to us when we really miss them.