Been selected for jury service three times now..
1st time didn’t get selected at all
2nd time had a case of buggery between 2 brothers that had happened about 20 years previously, not nice..
3rd time had a stabbing and also a injury caused be careless driving.
As other have said, take a book/big paper/kindle.. Casual dress code, nothing offensive on T shirts etc, jeans are perfectly acceptable.. Not sure about the canteen situation now, they were just closing ours on my last Jury service.
I enjoyed the experience, it was interesting to watch and be part of the process.