Well what do you know. I got home last night, turned it on and it works again. It's behaviour is different to before though - sticks for a long time at Starting PPP, then flips to a Stopped then immediately comes back with an IP address (sorry that was a bad explanation but I'm in the office now and can't see the machine).

I wonder if it's some sort of intermittent fault - shall just have to keep an eye on it - luckily I still have the old router to switch over to if it acts up again.

Tony