I thought I'd made this up, dodgy etymology and all!
I've been using it for at least the last six years. Would be interested to know where else it has turned up as I've never seen it online/in print.
I agree homocleide would be more consistent but I think it would be less comprehensible: the only English word I can think of that uses the Greek form is ophicleide and how many people have come across one of those?
I did try using homoclave for a while, which is, I think, more elegant, but I often had to explain it whereas people usually accept homoclef without asking further. Thank goodness our mongrel tongue has no fear of hybrid words!