Well... they responded to my request for SipBroker peering, saying "I've referred your request to the directors."... hmm... we'll see.
I also just posted a message in their user forums that may be worth keeping an eye on, or adding your voice to:
Peering, again...
In the meantime I've managed to cobble together a rather inelegant hack by call-forwarding Voipfone to a Gizmo/SipPhone number and then having that registered in Voxalot:
In VOIPfone control panel go to the "Set Call Divert" button, then in the box saying "Divert all calls to" enter your Gizmo/SipPhone number in this format:
*747xxxxxxx
Then add your Gizmo/SipPhone provider details as a Voxalot VSP, and set SIP register to "yes"
Like I say, it's not a great solution, but it does seem to work...
Cheers,
Ben