I was going to suggest that you must have a connection fault, Dan. As it is BT they will initially deny all knowledge, according to my experience. If you press them about it, they will check their end though. After that they'll deny all knowledge. Don't let them send an engineer out to you though. They'll try to charge you £65 for the privilege.
That reminds me that BT's latest advert, for their stumbling Home-Hub set-up, has a tag-line in it that suggests that...
...
unlike some others we'll never slow you down..!
What they mean is, of course, is that they'll never reduce the bandwidth allocated to you [called
throttling, in the trade]
, ie. reducing the Mb/s allowance to you. All this is a bit rich really, because BT used to be the biggest throttler of bandwidth in the whole broadband industry.