Is it worth putting in a quick call to the vet to ask for their comments...?
Nope. I've come to the inescapable conclusion that, with very rare exceptions, asking vets about anything but the basics when it comes to insulin dosing is an exercise in utter futility - at best.

As I've said before, I don't think I'd have been able to do anything like as much for Saoirse were it not for FDMB members and all I've learned here.
Numbers thus far today (Alphatrak):
AMPS - 10.7 then food plus skinny 0.5 of new vial of Lantus
AM+2.5 - 14.3
AM+3.5 - 17.2 - ate a bit then had a poop (one part tan, a bit gooey/marshmallowy and a bit whiffy.)
AM+5.5 - 17.8 - +1.5 postprandial. Mini-meal after this test.
AM+7.0 - 13.3 - +1.5 postprandial. Keen appetite and a good bit perkier. Fed after test.
I am wondering whether the new vial plus the possibility of the antibiotics starting to kick in might have resulted in Saoirse now getting too much insulin? Her curve is completely upside down. At times like this I wonder whether it may be better to have a cat on an in-out insulin so that one might respond more dynamically to rapidly shifting insulin needs; dealing with a depot in these circumstances is highly problematic.
Saoirse perked up a fair bit just after the AM+5.5 test. She was really hungry and ate well for me after this test. She's still stressy. Sitting on the sofa beside me but her tail is swishing like crazy.
Mogs
EDITED TO ADD:
@tiffmaxee,
@Chris & China,
@Marje and Gracie - if any of you are around is there any chance you'd have a look at Saoirse's numbers for me over the last few days, please? I'm at a loss for what to do about her insulin. For info, when I tried to take her up to 0.75 recently she became really lethargic and dysphoric; much like she was when she was being treated with Caninsulin. I'm thinking of asking the vet about switching Saoirse to ProZinc; I've got do something to sort this situation out for Saoirse. [ETA - further numbers below.]
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