I have a 53REG Megane 1.9DCI. Great car with no major problems so far (touch wood

)
However, I am experiencing a wobble problem when I'm braking, specially from high speed. It's quite bad as wobbles through to the steering wheel and my door mirrors shake aswell. Doesn't happen at low speed and when travelling at high speed and brake harder, the wobble dissappears.
Anyway, I'm having my wheel balancing checked tomorrow as the car does suffer from vibration when travelling at 70mph. Also, I should mention that I had all my discs/pads renewed last Oct 2008.
Could the wobble result in warped discs? And, by turning the discs over, can this cure it?
Any help will be much appreciated as I do not trust the Mechanics in my area as they can say anything with what the problem might be even if it's not
Thanks