It seems to me that this is not an agency. Rather it is a site, where escorts can join and advertise themselves. So it is hard to say whether they are serious or not. Some may be, some may not be. Why don't you check on sites like Cap69 if any of the girls are reviewed?
All I can say is that I recognize one of the escorts advertising on the Czech section, and that she is serious by reputation.
I must say, that Olga one on the Paris page is shit hot. Unfortunately also incredibly expensive.
If you find out more, please report.