I am wondering if this is a problem which is affecting more & more people.
I am with Demon and get a good service from them. I don't think they are up to any nasty tricks as I can often get a very respectable download speed.
I have noticed in recent days though, that a download from some single hosts seem to take ages - 3K with frequent stoppages! I have also noticed uploads doing the same in some cases, with the punter eventually disconnecting in despair. My upload speed is potentially 115K.

I have recently installed Peer Guardian after a recommendation on this forum. What a marvellous piece of software which illustrates graphically the quantity of nasty scrotes trying to upset P2P. Please install it and keep the snoopers and malcontents locked out!