I managed to get my i-mate SP3 to act as a modem for my Dell 620 laptop by adding the following modem initialisation string in the bluetooth setup dialog.
+CGDCONT =1,"IP","goto.virginmobile.uk", where goto.virginmobile.uk is the apn address as entered in the settings from my previous post, Setting Up An i-mate SP3 With Virgin Mobile Pay As You Go In The UK To Use The Internet.
I also had to setup a dialup connection using the *99# number with no user name, password nor domain entered. The network was set to Internet.
The access speed is pretty slow but it does work.