It seems that ADSL faceplates actually have RJ-45 sockets on them for some reason - don't know why, but they do.
Try terminating cat 5 or 3 pair telephone cable into a RJ-11 or RJ-12 plug, the cable is simply to fat to fit and neatly terminate.
(2 pairs twisted telephone cable or cat5 will terminate nicely into RJ-11 and BT431A plugs)
BT ADSL extension kits use cat 5 grade cable which plugs into the ADSL adaptor at one end and has a RJ-11 jack terminated at the other end.
It also lets you connect an RJ-45 patch lead for easy connection to structured cabling systems or simply to use as a decent extension lead with an inline adaptor to RJ-11.
6-pole Western socket
RJ-12 is the 6-way version of the RJ-11 which is 4-way. The connector size is identical however.
The only smaller connector I know of is those used for telephone handset cords - RJ-22 i believe being the 4-way example. Its simply a narrower version of the RJ-11. Do think there is a 6-way version though.
There is really no such thing as a "western socket" either, probably refers to RJ-12 as it is so common in north america and is used in Europe as well, notable Ireland. Most European countries however seem to have their own unique plugs, most of these are probably designed for 6 wires. Either for system phones on telephone switches or possibly as i think the case is in the US the different "pairs" of wires in an RJ lead can be used to take multiple lines down a single line cord, unlike here where we would use seperate sockets and leads.