Lovely video!
Noel, dont be getting too hung up on the chassis starting off, after all a real A is quite 'spritely' off the line too. As enniscorthyman says that recording is from 39 and she isnt pushed too hard, for a start she's older than IE's 071s or even 146, and besides an A really motors so its not necessary to push it as far, so that might be why it sounds tamer to you.