Thanks again folks for you kind words and thoughts, and so sorry to hear you've been through it so recently Joanne. It is truly heartbreaking.
I collected the wee guy from the emergency vet today to take him home to try and get him to eat. He's really weak and lethargic, and not interested in food at all, so I've given him a prescribed appetite stimulant and syringed a small amount of food into his mouth. He's still got it in him to use his dog door and go outside for a pee though!
He's snoozing beside me, much more content now than he was when I picked him up as he's at home, in a comfortable, warm, loving environment. I do feel like it's his time though, so he has an appointment at his vet ( his friend! ) tomorrow at 11am, which will be his final journey, if the vet agrees that it's his time.
I feel very, very sad, but it's hard to see my normally boisterous wee pal so drained of energy. I've been telling him that I'd love him to stay, I'll miss him more than words can express, I'll miss our long walks at the beach, the hills, the forest paths, exploring, just me and him. But I've let him know it's ok if he feels too tired to go on, that we are and always will be the best pals the world has ever seen, and that we will meet again sometime, somewhere.