Broadband user limits?

I appreciate that there are limits to the number of users that can share a single broadband connection at any one time but how does this work out in practice? At home I have 6 pc's sharing an 8m connection with no problems. A client has 32 users sharing an 8m connection with no problems - although they are 'casual users' rather than heavy users - so what is the thinking regarding limits? I ask this as a client who is moving to a new office has been advised by BT that a single line can support a maximum of 20 users. As he has a potential 65 users (Although about 40 of these are occasional, maybe a couple hours a week tops) they have told him he needs to have 3 seperate broadband enabled lines which is going to increase his costs by a substantial amount without even offering any real redundancy as all the lines will be provided by BT! Is this normal?

Most NAT routers onboard DHCP servers support upto 254 users i think it is.

Im not sure if the BT supplied routers have a limit on the number of users it will support but I'm fairly sure they can't limit the number of users behind your own router.

It might get a bit slow with a lot of users on though.

Yep, my thoughts exactly, the router will be connected to the network as will the PC's. Unless they are counting either internal IP addresses or MAC addresses I can see no way they would know how many users are simultaneously connected - and in any case it's no real concern for BT as far as I am concerned! To me the client has the choice of a single broadband for all 65 users and go slow when all of them are in use (Although the liklihood is that this will rarely, if ever happen or use 2 lines - 1 for the 20 or so permanent staff and the other for the 40 or so occasional users or any combination of the 2 but no way do I see 3 seperate lines being required!