a) Cornish pasties. It may never have occurred to you to eat a pasty, and, like retsina, they should only be consumed close to their point of origin. DO NOT be tempted to eat them in a pub or restaurant, or to buy them cold and heat them up. ALWAYS buy pasties hot from the oven from a pasty shop where they are made and eat immediately. It is worth paying the extra for 'steak' or 'premium'. They should be hot and peppery, and filled with potato, onion, swede and meat (veggie variations also available).
b) Cream teas. Are not a light snack - one between two is usually a good idea. The best are to be had in farmhouse kitchens and tea gardens. NB the cream is clotted, not whipped as in East Anglia.