You are all so kind and helpful. Thank you. I went along to his flat and as I knew would happen, he didn't answer the door and as his key was in the lock, I couldn't use my key to get in. I also tried knocking on the bedroom window to rouse him, but to no avail. I sat in the car and wrote a note, wrapped some money in it and told him it was for food and power, should he need it (I'd sneaked a look at his electric power-card box, which is on the outside of the house and saw it was down to the last couple of pounds). I then just had to come back home. Just back in the house when DS texted me, having switched his phone on when he realised I'd been at his door. He said he was fine, feeling pretty low, but that he'd 'survive'.
He was in a relationship for a couple of years with a girl who had a drink problem and they both abused substances during this time. He'd fallen for her deeply and since the break-up last summer, he's been on the downward spiral. He's made friends again with his sister (who unfortunately has estranged herself from me a few years ago) - I say made friends with her again, because they fell out after he made a mess of her house when under the influence of 'whatever' a few months ago. However, although she doesn't speak to me, she and DS have a close relationship and I'm so glad that it's being mended now, because she'll be very supportive towards him. The bottom line of it all, I think, is that he feels worthless.
After having received his text, I phoned him, just hoping he'd answer my call, and he did. Being able to speak to him lifted my spirits and I was careful not to ask him questions, but just to say that I loved him more than life itself (as we do all of our children, don't we), and that the GP would listen and give him the right support, whether it be suggesting more counselling or whatever he/she thought was appropriate.
After having spoken to DS, his dad and I went for a bit of a drive and a long walk. Just having a bit of space and bright, 'snow-shine' did help a good bit.
Reading all of your posts has helped me so much - not that I want others to suffer similar awful things, but just to know that I'm not alone in the 'fearfulness' that raises its head sometimes. Bless you. 