At around 23:00 GMT London yesterday, the internet connection to the hpHosts network went down. I spoke with the ISP and was told there were no problems at either their end, or any reported problems or expected maintenance at BT's end (though BT never told them about the work they were doing last time).
The connection came back around 02:15 this morning, but problems have developed with the network gateway. I'm currently investigating this to determine the actual cause, but obviously until this is resolved, the hpHosts server network will be offline. Apologies for the disruption folks.
/update 15:07 20-10-2010
The connection went down again whilst I was asleep this morning. I've spoken to the ISP again and it turns out the problem was with my local exchange (no idea what the problem was, BT apparently detected it at 0800 yesterday and evidently hadn't informed my ISP until today).
The connection is stable again, but I'm obviously going to continue monitoring it.