I have a Safecom 4-port ADSL router modem (wired) myself as it goes

So it is not do able using the BT modem?

I know I can plug one of these wireless access points into my wired router and it'll work, but I didn't know if you can or can't do it using a normal "1 connection" USB type ADSL modem...

I agree it's probably easier to get a wireless router modem and just have one box that does it all - like my wired one, except wireless. I ditched the Alcatel USB modem when I got my Safecom router modem and it's a lot better, since all my PC's have ethernet points.