Could anyone help me with my problem of steering  vibration under braking ?

The car is an r300d with the original tyres and  plenty of tread left on the fronts with 4000 miles on the clock. 

It seemed to all start after the car went to c Midlands for a service last year ....the car came back with wheels  incorrectly balanced ,car returned and rebalance better but not right then took it to another garage finally got the wheels balanced correctly !!!

But now I'm getting vibration when braking ???

what could this be ?and how to fix it ?

Many thanks David