Hi Tony and @sammyboy
I installed the "free" version of VoipNow server (
www.4psa.com) but couldn't get 3cx's softphone to work with it - the "free" Express Talk softphone could at least connect to the voipnow server (a virtual machine running CentOS 5.3) - just couldn't make calls to another extension.
I didn't install 3cx's server though - their softphone would work with that out of the box of course.
Oh well - it was a play platform anyway!
YMMV of course, but I think this is a great way to reduce costs within the office, but you do need to connect your voip server to a pstn provider to make and receive landline calls - if I haven't stated the bleeding obvious!
Cheers
Brad