Can anyone tell me what the problem is with my C3, each time l set the clock it resets its self, the key wo not keep it is coding.

Thanks
Colin

It is French, say no more.

Sounds like the small watch-battery-like battery that is within the electronics has failed. It is probably the car, rather than the key, that wo not keep its coding. You will need to take it to a Citroen garage and get it replaced.

Dunno what Stuart B thinks he is going on about but he is obviously guessing.

The key is synchronised to the BS l unit & once the BS l is coded with the CPH code it can never be altered or forgotten. The key however, can be reprogrammed with a different code. If the battery in the key goes flat this only affects the HF plip part of the key. The part of the key that is used to start the car & disarm the immobiliser is magnetically coded & requires no battery power.
For the key to repeatedly lose its code suggests the problem lies not with the key but either with a weak key aerial (common & cheap to verify) or with an internal BS l fault. The BS l wo not have lost its code, but it may have lost synchronisation with the keys & therefore be unable to recognize them, if the fault is with the key then it will only affect the one key, if all keys r affected then it is a problem with the BS l code reception.

l will not bother explaining exactly how the BS l & multiplexed networks deal with memory functions, but the fact that ur clock keeps losing its memory too suggests to me that there is an issue with the VAN+ remote power function.
This line carries no power when the car is on, but when the car is off it switches to 12v & is used to retain certain memory functions & detect network wake-up commands.
This line is fused with a 10amp fuse in the BS l (the fuses behind the wee panel in the glovebox).
l do not think the fuse will be blown, as if it was u would find the lights automatically turned on the sidelights & the wipers would automatically run on intermittent speed (backup function), therefore l think we can also rule out a power supply problem on this line before the BSI.
If the fault was internal to the BS l it could manifest itself on some networks but not others, & l believe that is what is happening to ur car.

This fault will probably require replacement of the BS l which will then need to be configured by ur local dealership.
To diagnose this problem correctly l would advise taking ur car to a good local dealership (Citroen UK own one of the Glasgow dealers), taking it somewhere else will cost u more money in the long run, as diagnosis of this requires a solid knowledge of the more advanced electrical architecture on ur car. l know this problem does not appear to affect complex systems, but appearences r deceptive, & anyone that looks at this problem & thinks it seems like a quick one obviously does not know much about how ur car works!

either battery flat or using fob on key out of range

Check your battery connection mine was doing exactly the same thing .
Went into citroen before l bought it they recoded the keys . Read the faults but did not check the basics.