NAO (National Audit Office) 1st round assessment

Has anyone already been on the NAO's 1st and subsequent assessment days recently?
Have got my 1st assessment coming up real soon and wanted some advice.
Is the maths test extremely similar to the one they send you? Is it a lot more/less difficult?
Also is the interview, more or less going through the answers on your application, or is there much more?
Any advice or help would be greatly appreciated.