If I was you mate I would replace the complete rack just to be on the safe side.

I can remember when I crashed my old 2i into a kerb, thought the only damage I had done was the bottom arm. Replaced the bottom arm drove it around for a few days with no problems. Turns out I had also weakened the steering rack (no signs of external damage) and the rack snapped in two resulting in no steering at all, you could spin the steering wheel round.

Luckily for me it broke as I was setting off from the lights.

If it had snapped at 70mph