Thank you so much, everyone, for taking the time to reply. All of these posts have made me stop, think and reflect tonight.
LegalEagle I've ordered the book (and another one besides) Recommendations are exactly what I need.
FabISGoing - I hold my hands up to not understanding depression. As I said, I alternate between feeling immensely protective over him and feeling quite selfishly that I am missing a partner and everything I'd hoped for in a relationship.
Solidgold Qestdom et al, I have known him for 10 years and there is not an ounce of me which feels he is a tosspot/selfish wanker etc etc. I genuinely feel he is either a. ill or b. just has a personality which means he can't cope with pressure. I could attribute it to his upbringing (quiet child, controlling mother) but don't feel qualified to speculate.
There has been SO MANY good posts on here, thank you. I am buoyed up just knowing I'm not alone
Progress tonight: I calmly told DP I would not tolerate being spoken to like that (when he threw a strop about something) and walked away. He told me I was an arse and I told him where the door was. Thereafter he was polite (although did not apologise!)
He then, after some persuasion, PHONED A COUNSELLOR HIMSELF and has an appointment for next Tuesday. After much huffing and puffing and what's the point-ing.
He has made some progress on the work he has to do, by me cajoling him off the sofa (lying with head in hands saying he was too stressed to do anything) and helping him reflect on what he needed to do, and drawing an action plan on a whiteboard.
He is now stacking the dishwasher, although there are a fair few 'for f**s sake' coming from the kitchen as I write.
Progress, I think?