Its not GA values its Abellio values you need to be looking at. Also Abellio are owned by NS based in Holland. I had my managers interview last week at Stratford and was fortunate enough to get offered the position pending the medical.
I received mixed advice on what to expect, some saying it would be very criteria based again others saying it would be an informal chat, mine was the later. The company research I did was invaluable and I felt it went down really well. You will be questioned on safety, responsibility and lone working so be prepared. You might be able to re-use some examples from the criteria based interview.
Where is your interview and what depot you hoping for? Im going to be based at Ilford, hopefully starting training on the 1st of feb. Good luck