Have you logged into the router to see what the stats are showing as? It may be that the line is on the edge of stability . Are you directly onto the main socket via a filter or are you using an ADSL plate?
Our connection has been rock solid of years but a few months back was up and down like a yo-yo every day, then it stabilised again and this week its back to daily drop outs in the morning, afternoon and over night. No changes on our end so either something is going on locally here or Sky are doing things on the exchange side.
