There are three types of people at your viva: those who will be there, those who might be there and those who may be there only if you agree.
Your examiners WILL be there. Every candidate in the UK has at least two examiners, typically one internal and one external. There are exceptions, but the majority of candidates will have two experienced academics examine them. Yours will have read your thesis, prepared and be ready to discuss whatever is needed at your viva.
You MIGHT have an independent chair at your viva. This person would typically be a senior academic from your university. They would act as an observer: no questions asked, no opinions given, except to confirm that the viva has been appropriate and fair. Not all vivas have an independent chair. It’s a good idea to check and find out if you might have one, so that you can prepare yourself accordingly.
Your supervisor may be present at your viva ONLY IF YOU AGREE. If they come they can only observe. No questions asked, no responses given. They could make notes on your behalf, but their presence might be stressful for you. You get to decide if they’re there: if you say no, they can’t go.
Oh! And you WILL be there. It’s your viva!