Reading viva regulations and googling about what to expect for your viva can only tell you so much. There are a lot of general viva expectations worth paying attention to – related to the format, the questions and examiners – but you also have to think about your particular discipline, field or area.
Two to three hours could be a useful general expectation for viva length. Your discipline might have a different expectation though, longer or shorter. That’s never a guarantee but it’s information that could help.
In general, PhD candidates don’t tend to give presentations to start their viva, at least not in the UK. But in some fields it is very common, an idea that has become a piece of “good practice”.
Your discipline may have particular questions or a focus on methods that isn’t common in other disciplines. You might not know that until you ask.
Pay attention to general viva advice and regulations, but also take time to ask your supervisors, friends and colleagues about their experiences and what they know about vivas in your discipline. Get as full a picture of what to expect as possible so that you can prepare accordingly.