Morning,
I'm a CSA at the moment and did these tests last year.
The best bit of advice i can give to anyone doing these role plays is to just relax. Yes, it's intimidating but if you've done customer service work before then you shouldn't have any problems. If you've not done customer service work before then, to be honest, it's just a case of manners and treating people the way you wish to be treated yourself.
My role play had something to do with delays on the line and step free access on to platforms. My customer wanted to get somewhere like Wembley Central from Wood Green but there were engineering works on the line. You have to apologise for the delays, explain why they are doing engineering works and then get her (or him) to where they need to go. I'm not giving anything away here as you are told all of the 'answers' by the assessors prior to the 'irate customer' coming in. Just stay as calm as much as you can, take your time and get the information right. As mentioned, they give you all the information/answers you need to get the role play right so you're already ahead in one department.
The numeracy and literacy tests are straightforward as well. Don't worry about them too much, just stay calm. When you get them, take your time, read the questions properly and double check everything. I was in a class of about 20 people and some of them just pelted through them and then afterwards realised they'd made mistakes.
If you get through to the final interview at the end of the day then make sure you have some customer related experiences to discuss. The interviewer will try to get as much detail from you as possible to a) ensure you know what you're talking about and b) make sure you're not fibbing! Again, try to treat it as a formal conversation about your experience to date. If you've not got that much work experience then try to draw on some life experiences instead.
All in all it's easy for me to sit here and type stay calm, relaxed etc etc as this is important to some people but i think it's key, especially when it comes to the role play. If you get flustered in the role play then they won't want you on a platform being surrounded by a load of people looking to have a go because Kings Cross is closed. If anyone doing this has quite a broad accent then make sure you slow it down and are nice and clear as well.
Good luck!