Setting up a personal VOIP net?

Hi,

I have a question about setting up a VOIP network. I will be living abroad soon so I want to be contactable for free at my new location. I have a spare landline telephone line at my UK (home) location, which I want to hookup to a PC with a modem and broadband internet, and I want it to answer calls to the spare line and put them them through to me abroad using VOIP, i.e set-up a connection to my laptop where I can communicate with them using a mic+speakers.

Any ideas?

Thanks!