Sorry, not in Sheffield, but do have questions for you... What is your network setup, wireless or any powerline adapters in use at all?
Also is BT your ISP, if not, what info can you glean from your ISP, any stats from them?
I made one of the four engineers BT have sent test from a PPP connection from his laptop directly wired to the VDSL modem using my ISP login, after I heard the conversation (typical, is it wireless, sounds like the customers problem, etc.) he was having with his helpdesk. So that rules out everything of mine! All their line tests from handheld kit report fine. So that points to exchange onwards.
No, it's not BT. I don't really want to mention the ISP as I (and them) don't think they are at fault.
Not got a lot of info from the ISP, other than it is probably a VP at issue. BT have to an extent acknowledged this six months ago, but no progress. Every time I raise the issue again, we seem to repeat over again, though BT seem to have stopped sending engineers!
All I know is that when the Sheffield node is reported as quiet, I get ok (not great) performance. As it is more utilised, but still with bags of bandwidth available, my performance is going seriously downhill!