Okay, here's what I would do:

1) Prepare for those tricky scenario questions - the one you got asked about difficult situations is very common, I got asked it lots. So you haven't worked in years, they saw your application and know that, so it's okay to explain you don't have recent work experience but instead give an example in your daily life (I used volunteering examples), what they are interested in is how you think/operate - they want to know what kind of person you are. Tip - they want someone who will keep calm and diffuse any conflict - remember the customer always comes first.

2) Think through what you will say about why you left your last job, spin it as positive as you can - do not be tempted to lay blame at your employer even if it's true, it will raise red flags for them. Say something like you wanted more customer contact orientated work - make it look as good as possible.

3) In group interviews they will be watching how you interact with other candidates, whatever your opinion of them make sure you communicate pleasantly - they will be watching for how you will interact with others. My present company uses this method and they are looking at your manner. Keep it light, breezy, make sure you smile and make eyes contact.

Good luck for Weds!