For Biometrics? From my experience of being lucky enough to get my call already and going with an appointment, I'm not sure it would be possible. When you arrive there are 2 seperate stages of security to go through who both have printouts of the days appointments and cross you off the list when you verify yourself. You need to confirm your identity with ID and your application number with your BIL.
I thought about doing it myself when I was waiting but after going through the process I know I wouldn't make it past the front door now.