When Auto lights are on, they will on occasion, whilst driving switch themselves off (!) and at other times they will go from main beam to dipped beam or again completely off. The only way to stop this happening is to switch them to manual. I didn't actually believe her when she told me
as every time I went to check them outside they worked OK (typical), until once I sat in the car with the engine running and waited for a while and sure enough, they went off with the display saying 'Info - Auto lights off' / 'Auto lights on' or similar. Major apology 
Main dealer couldn't find a problem as of course it is intermittent. I have checked the VOSA recalls and found that there were several for faulty sensor rings on the windscreen that needed replacing. Our car comes into the VIN range for this, but Citroen say this was done - but I'm not too sure - they seemed a bit vague looking at their records, so I left them with the recall notices and will wait to hear from them.
Meanwhile I've ordered up a Lexia Diagbox kit from Easydiagnostics yesterday, as recommended here by other members and will try and get it to see what is happening when connected up. At least I'll hopefully get some idea from this of the cause. I've heard some members talking about the Comms 2000 unit - but I've had no other issues linked with this problem occurring. It's also very low mileage for the year (30k)! so does under 2k a year. I would expect if it is the Comms 2000 unit that she would be getting other problems, but this seems very specific. Any thoughts from those with similar problems appreciated.