What constitutes a 'waxy potato' Potato salad, dauphinoise, sauteed, with potato cooked but firm and keeping its form with a wonderful waxy texture. Common all over France but a rarity in the UK. 

What varieties should we be looking for and where to find them?
As a rule, potatoes that are colored (red, gold, blue) tend to be waxier than white potatoes (red being the waxiest), and fingerling potatoes are the waxier than other sizes. A more complete list can be found here.