I phoned VM and spoke to someone in tech support who seemed to genuinely want to help, asking me to run pings, trace routes and nslookups (although I use my own DNS). After half an hour of sounding reasonably interested in fixing things, he advised me to restart my router :-(
As we were finishing the call and I was waiting for a reference number, the helpdesk chappie exclaimed "oh my system's just restarted for no reason!". "Oh, it's just like my TiVo box then," I said. "Different help desk..." came his response.
I spent some time this evening looking at broadband-only providers and Freeview HD PVRs. If Xilo are widely praised and offer a monthly rolling contract, they may well have a new customer...