I can't adequately explain how nice (for want of a better word) it was to see a medical professional who realised instantly that I am depressed because of all the physical health stuff. I didn't have to explain anything, or justify myself - he told me that it's very stressful to be in pain & in and out of hospital, & waiting for an operation to happen. He also told me that I can expect to feel very bad for a few days after the operation, as the combination of general anaesthetic + CO2 with my history of depression and chronic hyperventilation may cause psychological effects. Oddly, that cheered me up. I'd much rather worry about the likely risk of the anaesthetic making me very depressed for a few days than the unlikely risk of it killing me. I fear depression more than I fear death anyway, even though the former is temporary while the latter is permanent.
I did not get given any more drugs, but I have folic acid again. Megadose folic acid is a mood stabiliser, much safer than lithium - it helps a lot with labile moods when you're kinda ok but just keep breaking down and crying for no real reason. I suppose I'm lucky to have a GP who is remarkably knowledgeable about psych stuff - he knows more than either of the psychiatrists I've ever seen. Mind you, I wouldn't have ever needed to see him had I had a GP who knew anything about depression when I went the first time, four years earlier :/ Bah.