Now they've taken over the Telewest / NTL networks, Virgin are now advertising their "Talk Anywhere" service.
http://allyours.virginmedia.com/websales/service.do?id=3

One example is
For £20 per month you get line rental which is normally about £11 and 200 mins of calls to ,,,,,,,,,
"   * Landline UK numbers (they usually start with 01 and 02)
    * Mobile phones (starting with 07)
    * Non-geographic numbers (starting 08 except for 0800)
    * International landlines and international mobiles (all countries)
    * Dial-up internet numbers"

Obviously the more astute, and those with common sense, will continue to use dial through, unless you're a Samoan mobile.