Why won't my Xantia start?

Citroen Xantia 1.8 LXI petrol. Car has been starting and running fine for the last four years, except for a slight delay on occasion when trying to start. Last Thursday, the delay lasted for about 30 seconds before turning over and starting. Since then, nothing, car bump starts and runs fine, just will not turn over on the key. Battery is fine, starter relay is clicking as it should and I have changed the starter motor. Help please.