And I can add:
Voiptalk
Gizmo5
and Voipfone, provided that you set its diversion to *1*010xxxxxx, *1*031xxxxxx or *1*061xxxxxx, depending on your preferred server.
Sipgate doesn't work, although if you register it in PBXes and set it an inbound route to the URI
xxxxxx@voxalot.com it works a treat.