Thankyou to everyone who's been so supportive. Your kindness and the willingness to share information and personal experience has been a real help. I owe some of you e-mails or PMs. The feelings of being totally alone in this situation have dispersed.
We had a phone call from the vet this afternoon to say that Charlie's had a potassium deficiency, which has probably been the source of the fits and dithering, and for which he's now being treated. I feel slightly more optimistic than I did when I saw him yesterday.
Love. Courage. Forward.