Slowly but surely, Mr B has finally reached the point where he has an actual covering of fur on all his shaved patches. His forelegs & neck are much less noticeable & his tummy is once again all blond & fluffy (with spots, to contrast with the stripes he has everywhere else...), though the bottom half is of course rather less fluffsome than the top.
Thank you again to everyone who was so lovely & so helpful when he was so mysteriously!unwell in November, I really appreciate your support 
Actually, I need to chase vet about result of urinalysis I paid a small fortune to have sent away to a specialist Lab. My own (sadly much longer) stay at the vet in hospital shortly afterwards rather prevented my pursuing it, but I'm keen to know what it flipping showed.
But yes. All of the yays for my little cloud regaining his furry trousers, even if it is slowly. Still can't quite believe they managed to shave him & do the ultrasound without sedating him. Glad, because while obviously the drugs are safe (etc) I'd rather the cats not have them if possible (& wouldn't it be awful if they were like me & IV sedation made them want to fight off the people doing the painful & unpleasant things to them?!) but also I hate the idea that he was just so paralysed with fear they could do whatever. I shall have to tell myself he was just on his Very Best Behaviour & Being A Good Cat as instructed. Unf.
But again, hurrah for the return of Mr B's fur. And hopefully the antibiotics cleared up whatever was going on & the urinary tract health supplements that he will be having until the end of time, possibly (it is a HUGE box) will ensure he stays ok.
(As I write this he is snuggled tightly against me, having a thorough wash & giving his claws a trim. Looking as good as he does takes work...)