I use VONAGE.
They charge just £7.99 per month, and you get unlimited calls to:
- Any British Landline (01, 02 numbers)
- Any American Landline and Mobile
- Any Canadian Landline and Mobile
You use a normal phone, which is simply plugged into your router. There is no need for your PC to be on, and no need to use PC style VOIP phones.
In addition, you can set it up so that when someone rings you, it will simultaneously ring up to 5 other normal numbers at the same time.
When you sign up, you can choose which dialling code you would like!
OR Just £5.99 if you dont need to call abroad.