Ouch!
It doesn't really rise much, the air that is in it creates the light and fluffy merainge inside but doesn't tend to make it get bigger. You need a raising agent for that.

Did you mix, mix, mix to make sure the sugar had dissolved properly?
Did you build up the shape of the pav as you wanted it on the baking tray (nice high sides) before baking?
Did you turn off the heat when it was done, open the oven door and let it cool in the oven for an hour?

Can't think of anything else!

BTW, my mum the Pav Master swears by not adding cornflour - ever, but throwing in a dash of vinegar (preferably raspberry). I can never match my mother's pavs!

Anyway, take heart, you get to do it again now! More bowls to lick!