You can adjust the torsion bar at the back of your car to lower it, the thing is getting it right. I lowered my car last year. The front end is easy, but getting the back just right was a bit of a trial and error.
I adjusted the torsion bar by 1 spline, but this lowered the car about 100mm. So while putting it all back together (to let someone else have the headache of doing it for me), I noticed that the splines on the inside of the torsion bar are tighter, so I adjusted it using the splines on the inside of the torsion bars, and hey presto, I got it set up just right.
I had an old Maxpower mag that told you how to adjust torsion bars on a 5gtt, So I set to and did it myself.
Now my car sits 60mm lower at the front, and 70mm lower at the back.
Dave77