So pitiful. :-(

Well Simba, Monty and Bubba are off to the vets shortly to be "done" and they are meowing and crying for food and can't have any. They are all over me, pleading to be fed, in fact if I say Puss in Boots from Shrek you can imagine the scene. They are searching everywhere to try to find food.

Puss in Boots is always amusing.  I loved where Shrek first met him and he coughed up a fur ball.

They will be fine.

Can anyone tell me how long after the op do they start calming down? They are running around like fools, trying hard to keep them calm. Bubba is the calmest of the lot, Simba and Monty are being as mad as normal.

Ah, well, it "calms them down" in that they don't have to expend energy with sexual behaviors. . .but if it's just normal crazy kitty running around it won't really make much difference .

Willowy, they acting up worse than before the op, in fact not long after I posted, Bubba had pulled a blanket out of one of the activity centre hides holes and was lying on it under my legs and I went to stroke him and he bit me on the back of the leg, luckily it didn't break the skin, but it was sharp.

I'm sure by now your kittens must be settled down, but from what you say it sounds like you were seeing them still under the effects of coming out from anesthesia.  Each time one of our foster litters has come home from being fixed, they are way out of sorts--mean, growly, aggressive.  I've sometimes had to keep one or two of the worst in their carriers or in a separate room for awhile until the anesthesia effects wear off.

Whoa! They will calm down soon

Yes they have calmed down now, in fact Bubba has even started lying next to me and sleeping, something none of them did before.

Thats exactly what happens. At first they are so peed for you leaving them. Then they settle and become sweet hearts