this might help you
NetBalancer - internet traffic control and monitoring tool
you can effectlvely limit the bandwidth available to the browser you are using to access Lovefilm to keep it under the HD switchover point.
its free for the low spec 5 process version so you can give it a go and see if it works for you.
As per teh other s though to sell you a super fast connection then limit it to as little as that when their own ads sell on the streaming video ability is criminal IMHO