Ok, usually you topple over to a spinner when you have got the length wrong, either by being beaten in the flight or by going forward to a ball you could play back to.
The key is to play the ball late, but also not to over commit, you will have a moment to react as the ball drops or dips (depending on the quality of the spinner - a really good spinner will make the ball dip and shape late) so ensure you don't play the ball outside your natural zone - hold your shape - and definitely don't push at the ball.
Two ways I have seen of playing this (I am sure there are others) are the VVS way (probably the best player of spin of his generation) or the Duncan Fletcher "forward press" way - Tresco is the ultimate exponent of this method.
VVS plays the ball amazingly late with wonderfully quick wrists (a bit like AB De Villiers or Michael Clarke).
I have posted comments elsewhere about playing spin, so going back to your balance issue, practice shadow batting, but leeding with your head and letting you foot move second, you will then play with the bent front leg, aluded to above.
I hope that makes sence, ask if it doesn't or disagree!