Just thought i'd add my insignificant opinion to this thread regarding the mental illness/depression aspect. I think once, as in this case, a doctor is prepared to declare that you are suffering from depression then the cat is out of the bag. You either don't go to the doctor in the first place or go but accept the diagnosis, you don't really have the luxury of choosing not to inform the CAA. It will be in your medical notes should an employer request to have access to them and you have to commit perjury at every medical renewal, which if it ever came to light is the end of your career. Secondly, if a person is depressed should they really be encouraged not to seek help and disclose it to the CAA? We work in a high pressure, high stress environment and need to rely on other people, if someone is hiding a problem then it can present potential issues for flight safety and for the further wellbeing of that crew member.
As for the 18 month time limit thing? Bit of a kick in the balls, 18 months is a fairly long time however i have no wish to kick a man when he's down, my advice would be to take it on the chin, retake them and get them out of the way in two or three month.