It went rubbish for me..lol. I completed the form for the agency, they sent me an email saying that I have been successful to the next stage and I had to ring them. I did, and was asked a few questions, non interview ones, such as height, illnesses blah blah blah. A couple of days later I received an email saying I had not been successful. There is no way I wanted to go through an agency, the sole reason I did was because the EY website crashed on me several times and then locked me out, which meant I could not process with my application and even asking their IT Dept to sort it out was like me banging my head against a brick wall!
I would advise that you apply to EY on their website, forget the agency. Since you have already applied through the agency, there is no harm I feel in applying directly with the company as I think your chances are higher in getting a call.
Good Luck