The problem with remote fobs is that people always use them and never physically use the key to lock and unlock the doors. This means that the door lock tumblers end up seizing due to inactivity and you don't realize it until it is too late. The only fix now for this issue is to replace the door tumbler.

In the future, ( and this is what I do ) lubricate all the exterior key locks at least once a year and use them periodically instead of the remote fob. This will keep them from seizing

Jay is basically right though it only seems to affect some cars. Each of the tumblers in the lock have a very tiny spring behind them and lack of use can cause them to siezhe up, though rarely all of them. Some older Peugeots can be prone to it and on at least one model the lock barrel with the key in it will just rotate freely without doing any thing. That is actually an anti theft thing and [though it is just mechanical, effectively the lock thinks a wrong key is oin it]. Try WD40 squirted into the lock until it stants dribbling out. Work the key in and out a dozen or more times then leave it for a couple of hours. You may find that it then works as usual.

The remote may need programing as for the outer door lock/cylinder lack of use could cause the problems you have,try squirting some wd/40 in the lock with the straw and work it in with the key

^^^^ Jay is right

so basically couple of months ago i regrettably purchased a citroen c2 privately which has completely screwed me the day i got it and he knew i was pregnant!

anyways.. besides all the other problems with it, the key is my major concern. the remote on the fob doesn't work and i've tried changing the battery but still no luck? plus its a new key fob which the owner before had purchased and was 'working' according to him. the interior lock inside does work though so it can't be an electric fault?

but also its a pain to lock it manually. the new key doesn't fit in the keyhole at all so that's useless, and the spare key does fit in but it took like 10 mins to be able to lock it or unlock it manually which only locked the drivers side and not the passenger side nor the boot! we have found a way to lock all doors by pressing the interior lock whilst the window is going up which i've never dared to do! BUT the other day we tried to unlock it with the key and now it simply won't unlock!! :'(

any suggestions? as i'm really stuck on what to do as we cant get into the car at all now =(