I'm powering off everything as I swap things around, but it's not made any difference. India's suggestion (use a proxy) made it go from 3.7 to 2.5

Needless to say, I've removed that again now
I've tried it again today, but still no difference. I've also tried with Norton AV and ZoneAlarm switched off and that hasn't helped either. I'm checking the speed using the Speed Test from this forum.