I have a 2009 Citroen Berlingo that has starter issues. The strange thing is when the car is cold ie: 1st start in the morning, it starts perfectly (no sign of strain at all) but drive it around for a while and then when engine is hot, it wont start....just click click. Battery just fine and alternator just fine (according to breakdown service).
I had this on one of my Ford cars in the late 80's I realise things have drastically changed but its worth a thought. Change the starter.
Same symptoms as yours and it was the field coil fault in the starter draining the battery but not pushing out power the other end to the flywheel to turn engine over when hot but worked fine like your s when cold.
Worth a shot in the dark be lucky.