As a previous poster mentioned if you have a PPL you should basically be able to do a few hours dual training and then be granted a G2 allowing you to fly solo to build up a bit of time on type. Once you have the required hours you'll get some further training and a quick checkout with the boss and you'll be able to get cracking as a G1 taking cadets on Famil flights.
Without a PPL you'll likely have to start at the begining and if its anything like the VGS I used to fly for staff training time was getting fairly limited, there were a number of staff cadets struggling to get much flying. It also tended to be that any new PPL CGI's that started got priority so they could be brought up to G1 standard as quickly as poss.
Saying that I really enjoyed my VGS time and I'd reccomend it to anyone......