The Old BT guy is quite right about fitting Master Socket. This the 'demarcation point' between you and BT and only BT should fit them. However if you have a modern NTE5 Master Socket is is perfectly permissible to fit a new faceplate, for ADSL (Broadband) for example.
However here is some clarification on connecting extensions: Connect the mainly Blue with White wire to 2 and the mainly White with Blue to 5. Connect NO OTHER wires. 4 has never been used. 3 hasn't been needed for donkeys years because modern phones do not need it and, as it can affect broadband, it should not be connected. (I guess that the Old BT guy has been away from this for a while.)
If you post a NEW question explaining what you are trying to achieve, I may be able to help further.
t
October 2008