Drivers door lock

[Be-Exer]

Hi again - Can anyone give me a bit of advice with my Xantia lock cylinder?
I can't get the key more than one third in and am trying to get the cylinder out to see if it can be fixed. I see that Haynes say to remove the grommet in the door edge and push on the clip - which I'm not sure if I can make out properly. As I can't insert the key am I wasting my time trying this method? I know with some ignition locks that unless the key is inserted it is impossible to operate the release mechanism.
Beyond this, what am I looking/feeling for by way of a clip on the cylinder?
Thanks in advance for any advice

[Be-Exer]

An update for anyone who has the same problem - You don't have to have the key in the lock and there is a slot in the door handle moulding inner that allows you to push the lock out once the clip is depressed.
When I got the lock out I carefully took it apart and found - as I suspected - that the problem was with the dust cover flap. I teased that out, reasembled the lock and swapped this one over to the passenger side as they are not handed. As it's not ideal being without a dust flap I covered the the key slot with a scrap of insulating tape which can be removed in the (rare) event I need to use it.