> I am a new psion 3c user and I would like to know what Leads & plugs I
> need to connect my 3c to a standard external modem (not the psion one - too
> slow)

 a) PsiWin RS232 cable (as supplied with PsiWin)
 b) Psion modem adaptor 
    *OR*
    Homemade nullmodem adaptor, see my web site
 http://www.alcatel.ch/
 http://ourworld.compuserve.com/homepages/Jochen_Siegenthaler/ (click above)

> (not the psion one - too slow)

Note that there is no point getting anything faster than a 14400 modem as
the Psion processor and TCP/IP stack cannot handle much faster speeds.
The speed bottleneck is the TCP/IP stack, and not the modem connection.