You can bring things with you, such as books, knitting or paperwork, to(Scroll down to 'Facilities in the pool room')
occupy yourself while you wait.
my knitting was promptly confiscated as I entered the court building.
While I realise this is consistent with the policy of airlines, I was a bit annoyed as I had specially checked before taking my knitting. And it is not just the website; it's in the official handbook for jurors which they gave me after taking away my knitting. Apparently if you are selected as a juror you can bring in the knitting for when you are not actually in the courtroom but I don't know if I want to test this.
Lucky I had brought a book.