You don't need to remove anything but the knee bolster to replace a 16V's speedo cable.

You might have one of the multi-plug connectors loose. Time to pull the whole cluster and take a look-see.

I usually remove the steering wheel when removing the cluster, but if you don't completely remove it, you should be able to see behind it if anything is loose/disconnected without removing the wheel. Just disconnect the speed cable and pull it towards the steering wheel.

Tinker