Dear Poster. I have got the same problem in my charade. 2 years back it used to brake in a straight line. after that dont know how and why it started tailing on hard braking. Even i got shocking near miss due to this braking problem. I have spent around 15k on it and countless precious hours but the result is nil.
After much study and googling i have got a way out to identify the problem (i have not yet tried this coz i got transferred to Mirpur mathelo).
First, you need brake pressure testing kit. Ready made kits are costly. you can make it as per your car's brake nozzle size. you will have to unscrew the bleeding valve and attach this tester and press brake to measure the exact pressure coming to individual tyre. If you get any difference in measurements, you will have to work back by testing individual equipment in its way on that specific tyre.
This is the only way i have worked out to solve this mysterious, unsafe, dangerous and life threatening brake disease.
You can also throw another arrow in the dark, by replacing brake pressure distribution valve.