We hada diabetic cat that went though a terrible week with trips to the vets and hourly checks etc and barely pulled through, when he started showing the same symptoms a week later we figured it easier for him to spare him all the trips and tests, we made him up a bed in the travel basket, and supplied him with food and water - he was obviously getting worse by the hour, and had constant company from one of the other cats who went in and curled up with him, and passed peacefully to his rest in the midst of his human and feline family, he was the only one that none of the cats went searching for after he had passed, its as if they all realised what had happened, when others have been taken to the vets at a similar stage they have always spent time calling out and searching the house.
Bagpuss is now resting and no longer suffering, with time all the memories will be the good ones and you will grieve less, but its always painful at first.
Grendel