I agree the banks are quite usefull as well as Businesslink. Your college course may only need a demonstration of your understanding, eg work out the population, divide by two, take a % of what you think the client base would be, then work out a reasonable number of treatments. Even paid for market info (which is very difficult to get hold off - as per Geeg) is out of date. Check your answers by multiplying the number of users on this board by an average number of clients and see what figure you come out with!
Good luck - don't get too bogged down with the detail - you need to demonstrate an understanding of this not absolute accuracy. I appreciate it needs to relate to real life but there is a balance.
Let us know if you pass!
Cathy