I thought I would share my progress - I think it is good to report on the better times as well as the bad.
I have broken through this spell of depression - having denied myself medical treatment all my life, I am now approaching 4 weeks on 100mg sertraline. I feel a different person and I genuinely can't remember ever feeling this "normal". I owe a huge amount to the community here that held my hand and helped me with the wake up call I needed, I can't thank you all enough. In particular one person made me re-evaluate my life and has given me extra hope for the future (you know who you are Silver).
I won't kid myself that I am "cured" and I will be back for support if and when the depression returns.
In the meantime, I intend to hang around here and help where I can. Thanks again all, I probably owe you my life.