Hello,
I bought one a week ago and have fitted it fine, is it a META remote central locking kit (the one with the yellow relay with a wire coming off it)?
I have a mk1 Punto and you simply go into the glove compartment and in the top of it you will see a flap that comes down when you move a plastic stopper. This is easy to do so take a look.
In here is the yellow central locking relay simply remove the exsisting one and replace with the new one.
The new central locking system does not affect anything, and the key can still be used to lock and unlock the vehicle.
The instructions; these were a bit dodgy as they only show pictures and contain no writing, i think its so they didnt need to print them for different languages.
Hope this helps! If you want me to take some pictures i will do.