Used to work in this area.
Agreed that there is a LOT of waiting around and being brought in and out of court. Take books, puzzles, etc as it can get boring. Bring extra snacks for break time as heard some courts offer lunch money that doesn't cover a huge amount.
There's no need to dress smart. I mean, don't go in pyjamas, but general weekend wear is fine. many courts have very hard wooden old fashioned bench seating, and even in the more comfortable ones you're sat straight upright unmoving for hours on end. Comfort is key. You're just going to be fidgeting and hot in a blazer, shirt and tight trousers, so wear what's comfy.
Someone asked about a day off during a trial - you're unlikely to get one on a short trial. They tend to only be given on long trials and after several weeks, only if absolutely necessary. They wouldn't give one day off in a three day trial - they'll either not choose you or remove you and carry on. You having a day off isn't you alone - the whole trial will have to halt for the day as the entire jury need to be present throughout. If you have a funeral to go to, tell them at the start of your service. They'll hopefully defer you to serve another time.
Once saw a juror who thought she could just have a duvet day and "catch up from the others" the next day. Needless to say judge wasn't impressed and had her promptly brought to court!
If you have holidays etc booked, take ALL info and flight confirmations with you on your first day. That means you'll likely be excused if there's say a 6 month long trial they want jurors for. Same goes for those with (genuinely) no alternative childcare, the self employed and those whose work couldn't spare them for that long. (As an aside, once saw a "famous" soap actress get her service deferred as she had "some very important storylines coming up" 😂)
Number one rule is DO NOT Google the case or defendant or post about it on social media/talk loudly outside court surrounded by the defendants family, or decide to send a flirty Facebook message to a copper giving evidence you've taken a shine too... unbelievably I've seen all this happen (not that you lovely MNrs would do so) and it's led to million pound trials collapsing and jurors being held in contempt of court!
It's not always doom and gloom. Many judges and barristers will try to explain it all and make you comfortable. Follow the judges lead and not what you've seen on tv on how to approach the case. Good luck!