Bagpuss: First, I just want to acknowledge your courage in coming "out" with your depression. Like Skipjack, I am married to someone who suffers from depression; like you, I am a firm believer in a "better life thru chemistry!" He is a writer, and his worst times are when he can't even bring himself to journal, and the rest of the family suffers as a result!
Secondly, I'm also a singer just beginning to seek a band. I live in a small region, far from big cities, where there are plenty of folkies but few venues other than kitchens or contra dances! So, I have just barely begun to spread the word of mouth that I'm interested. There are no sessions here that I know of, but there must be some in Leeds, and I think that's great advice!
Last of all, just put it out there that you want this, tell others, keep practicing and building your repertoire of songs and tunes that interest you, and if you keep at it, it will happen. Best of luck and blessings on the way!