Has any one got instructions how to fit and wire up a Link knock sensor with a Bosch sensor?

 

It usually comes with an inline plug and socket.
It needs live and earth connections making, the sensor bolts to the top of the engine block.

Dead easy.

 

What happens to the original wires or plug?

 

Um...as has been said. It has live and ground connections, plus connections to the knock sensor (ground and signal).

Basically, a 4-pin connector: two grounds joined internally to the knock link; battery; knock sensor signal.

 

That's it.

Mine has a large 4-pin connector about 600mm from the box, then about 2m of wires coming off that.

Two of them go to the sensor, via a fancy plug, (avilable from various places), and the others to ignition live and earth.