After three years of being without the central locking on my car , I have now cracked it.
This afternoon I found a site called Xantia World and on their menu they had a heading called
Check Point,which gave a list of faults on Xantias .As I started scrolling down all the usual faults I got to the last one there it said" If the Plip is working but the central locking still will not work disconnect the IR receiver and then reconnect it"but I had tried that at the start,but not with the ignition on.So I disconnected the IR in the roof switched on the ignition , switched off the ignition reconnected the IR .It resets the IR.
I then got out of the car pressed the central locking button and.......................it worked.
I had not seen this solution on any other site.
So if your Plip works and still no central locking give that a try .
H