Having gone through my fair share of disconnections, poor speeds (<0.5Mb) etc my line seems to have settled down. Even so my router was synching in excess of 5Mb but I was only getting a reported speed of 3Mb
I tried the following (which has been widely discussed)
if you see that your hardware is reporting a higher speed, you will need to connect at that speed at least once a day for a 3 day period to automatically update your connection speed.
It really does seem to work - this switching off once a day. After a few days where my router was reporting synchs of ~4500, my max speed setting had dropped back to 4000. I've turned off overnight, then on first thing in the morning when I seem to get higher syncs (around 5800 - so assume there's less contention then) and now my max is reporting 5500 tonight.