It's the mobile aspect I'm particularly interested in but calling the UK from a Swedish landline is also appealing. I've had a SkypeIn number for ages and the quality ranges from perfect to unusable so I'm looking for an alternative or at least something I can use alongside it.

Operator One looks dearer than Skype but much cheaper than Telia or BT. I've got 2 euros to experiment with by signing up and Liking them on Facebook. Swedish mobile and Swedish landline to UK landline both worked well. Mobile to mobile will be the real test for me as people in the UK have often failed to understand a word I've said when I've left mobile answerphone messages using Skype.