My heart's with you Kev.  I had the same experience with Buster, our 25 lb. Siamese who thought he was dog.  Kidney failure got him at age 12 and he went quickly and quietly into his next life (hopefully as a dog).  I cried for hours.  I didn't even realize how much I cared for him until the vet carried out his duty.  To this day I can hear him stalking in the bedroom, waiting for the inevitable very heavy bounce onto the bed.

We've since adopted 2 rescued cats and 1 rescued dog (who all happily seem to accept their given species), and I applaud everyone who saves an animal from the needle or worse.  I'm happy to see that so many on this board seem to be of like mind.

I wish I were 1/2 as good a person as my dog thinks I am.

Paul