Hi Stuart,
There's a link in my signature about the wonders of upto 8Mbps broadband which might be quite helpful for you.
Basically, you've had a blip in your synchronisation speed. That's the speed of signal between your router and the exchange. When this happens, BT lower your speed profile down to a value near the low sync event. now that you're syncing at a higher level, your speeds will rise, but this can take up to 3 days.
