I don't think a broken cable can do this, the lever is quite a self-contained assembly. It moves through a quadrant with a spring-loaded ratchet that never allows the knob to 'come flying out'. So the most likely failure in my opinion must be the ratchet itself. May as well get another lever off a scrapped car, they are not a common failure. But you will have to take out the seats and carpet. Before the seats will slide out (rearwards) you have to hammer-in the tabs inside the seat rails.
While you are there, you can improve the lever as follows.
Unbolt the bracket from the floor (two bolts). You will probably find that the captive nuts have torn away from the floor.
Take out the pivot pin (thin clip in the shape of a ring with a break in it)
Push in one or two thin washers so that the lever is a tight but smooth fit in the bracket. Grease it, and put the pivot pin back in.
Get two thick washers about 3-4cm in diameter with an 8mm hole, also two 13mm (across flats) nuts and some longer bolts to match.
Install washers under reinforcements in bodywork seemingly intended for the purpose, yet not used (the sheet metal with captive nuts sits on top of the reinforcements instead of underneath!)
Get an assistant to help with fitting the lever bracket with bolts through the thick washers.
My handbrake lever feels 100% better and no welding etc. was required. In the past I have added extra tabs to the lever bracket (in standard form, the tabs are optimised for left-hand-drive). But now, I don't think it's worth the trouble. Just add the washers (you should even be able to get the plastic cover refitted reasonably well underneath).
-Alex
