Crumpet did you not hear about TalkTalk? For £21 per month they give broadband internet of up to 8Mb and free (zero cost) calls to fixed phones in the UK, all EU countries (and a few more European countries), USA, Canada, Australia, New Zealand and several more international countries. To the USA and Canada calls to mobile phones are also free.
I see only one problem with that deal, they only give you 8Mb of data a month. You'll chew that up within the first hour, what do they charge after that?
My advice would be to go with Skype, just download the program, plug a microphone into your souncard (headset is prefferable). They do have a number where you can test your audio, you'll find it easily you just talk when prompted and it plays your recording back so you can hear how your connection is etc. You can search for someone on skype by using their email address as well, in fact thats how it works, you're not given a number.
That's pretty much it!