Despite some annoying initial problems, I’ve been successfully using Tesco’s Internet Phone service since May of last year. This is a SIP-based service, costing £2.89 a month, that provides me with an additional phone number (in my case it appears to be in Southampton) and up to 3000 minutes of “free” calls to UK geographic (01, 02 and 03) phone numbers. Given that my main desire was for an inexpensive second line, it’s a pretty good deal; around half the monthly cost of any of their competitors, and devoid of the plethora of startup and termination charges that (say) Vonage impose.
In combination with my VoIP capable Siemens DECT system, it’s been great.
Unfortunately, as of the 27th April, the service will be closed down. Which is most frustrating. So now the hunt starts for a new VoIP supplier that offers a broadly comparable service.