Robinw - thought I'd add a 'maths' message on this, rather than starting a new thread. Have you found sites to suit your dd? How old is she? And what sort of things are you looking for?
We find playing lots of games at home, like Yahtzee and Monopoly, have helped his mental arithmetic, and we also play doubling/tripling games in the car, and making sums out of car numberplates, etc.
Not sure if this is the level you're thinking of. DS1 is above average in Maths, but it's not his best subject, and he is only 6, I think your dd is probably much older?
Do let us know what's worked for you.