Hi Digston - Thanks very much for replying. I appreciate you taking the time to read through such a long post.
I put a call into my vet's office, and the receptionist said he's out on an emergency call right now, but will ring me as soon as he can.
Yes, Bindo's 'back end' does smell pretty awful. I hesitated to go into that in my introductory post, as it was already very detailed and was heading into the territory of 'off-putting reading', so I held back on the smell part. Poor Bindo's been trying his utmost at cleaning himself (in that area) constantly (which also worries me - by doing that, which I realise is instinctual - could he be making himself worse by ingesting what's coming out the other end of him?).
But even after his cleaning/licking himself, and me (very, very, very gently) wiping the area as clean as I can, the offending discharge has returned. Not immediately after cleaning/licking or wiping him, but it does start oozing out again, and yes, still smelling very badly.
Is the diet that your cat has been put on helped him? Has the discharge stopped completely?
Thanks again for replying. Now it's just a matter of playing the waiting game, until the vet gets back to me.