I saw a couple of VIP girls when I first started punting. Quite a few WGs join his agency when they start, but in my experience they do not stay there very long. Most seem to set up their own profiles, although if Bella has done so then I have not seen it.
The problem is that VIP/739 girls are around £50 per hour more expensive than their competitors, due to the agency's hefty cut. Once the girls realise how much more business they would do if they dropped their prices, they are off to work as independents.