To clear things up:
My depression has been diagnosed as such by a doctor.
I've had several episodes of depression in the past and after seeing my doctor I have arranged counselling sessions which are starting this week.
I informed my boss this morning about the situation, if only to ensure that she knew why I had requested a morning off this week for my initial session (a request which had already been okayed).
I have been working for the company for just over 3 months which does complicate things from a legal point of view.
I'm not willing to name and shame the individual or the company involved but I want these issues to be openly discussed in a public forum as millions of people suffer silently with mental health problems and should not fear repercussions from their employers.
In short, what happened to me today has happened to others before me but if I can stop it happening to someone else in the future then I can feel like something positive can come from this.