I've done this, but for an ISDN line, not ADSL. I imagine the same principles apply though - the key bit of kit is a single box which combines an Ethernet hub, router and ISDN (ADSL in your case) terminal adapter (ie modem, although technically it's not a modem
). My setup's not wireless, but I guess you would either buy a wireless hub/router/TA, if such things exist, or just plug the normal wireless receiver thingy into the hub/router/TA.
It took a bit of setting up but was basically straightforward and extremely convenient. The hub/router/TA does dial-on-demand and can be programmed to drop the line after so many seconds of inactivity, dial up on the second ISDN channel if the first one is busy for more than so many seconds, etc etc. I now have three machines that can connect to each other and the internet all at the same time, sharing the connection - well worth doing.
cbl.
ps I'd upgrade to ADSL myself but such high technology hasn't reached my part of East Kent yet!
Edited to add: My hub/router/TA is an Arescom Netlinker - they don't appear to make them any more, but they do have the ADSL equivalent, which is what you need - see
their website for more. I don't know anything about BT's kit but I've had no trouble at all with the my Netlinker...