When I did my exams the only place to store any belongings was a small cloakroom, for everyone. Plenty of people brought iPads and laptops thought and there were no issues. Last time I was there there was a bit of renovation going on so it might have changed.
I would say your calculator will not be questioned or given a second glance, if its a standard looking scientific calculator that doesn't look out of the ordinary (which I am sure as a 8x casio it is pretty common looking) then it should be fine.
HOWEVER.
If it was me I would get an approved model because I would not want even the slightest bit of extra worry or stress.