"if you live more than a mile from your local bt exchange dont bother having bt broadbrand its rubbish"
Which, in fact, could apply to any ISP down a copper wire, depending:
* the state of that wire
* local contention ratios
* whether or not the ISP has its' own equipment in the local exchange
* note also, that BT promised you "up to" 8mbps - as do all copper-based ISPs