Hi
Induction Day (based on mine in 2012) - sitting on your backside for about 90% of the time. Listening to a couple of people tell you about the company, watching several videos. Very little about doing the job itself. Maybe a wander into the mail centre to be shown how to push a York (large mail trolley) around, how to pick up something off the ground (bend your legs, not your back). Wear smart, comfortable clothes - clean jeans, trainers, plain t-shirt etc. The Induction Day will count as part of your working week, so check that you are paid for it and any overtime it may cause.
Hours - the only real way you'll know is when you turn up! Royal Mail are very good at advertising jobs with certain hours, then expecting you to change to whatever they actually need you to do. Chances are the finish time will be extended in the early days as it will take you longer. You say 30 hours over 5 days, so it will be 6 hours on each day - so it may be 6 hours between 8am and 4pm, our place would be 0830-1430.
Union - personal decision. Probably worth having as someone to turn to if you have problems, but it can depend on how good the office rep is. You will be paid weekly and the union fees taken weekly based on your contracted hours. You can opt in or out of paying a small amount extra that goes into the political fund - personally I don't pay that bit as my politics are my business.
