Note Make the meringues 2cm smaller in diameter than your serving glasses. They'll expand slightly during baking to fit on top of your serving glasses.
The size of your serving glasses will determine the size of the meringues you'll need to pipe to fit on top of these little individual pavlovas. In any case, it's okay to crush the sides a little bit to make them fit. Or you could serve this dessert like an Eton mess, crushing the meringues and folding them through the cream and blueberries to give a ripple effect.