Thanks for the compliment re my website, but it does need several significant updates for later broadband developments. I don't wish to explain why I haven't done them, but I ought to get on with them.
Re the fact that the test says maximum achievable 7.15Mbps, which is correct for the 8.13Mbps (8128kbps to be precise) sync., but the IP Profile is stated as 6Mbps, we appear to have a situation I have seen Plusnet senior support staff detect in the past from some test ISPs can do. I don't know what that test is.
They call it an IP Profile imbalance. (Nothing to do with the Plusnet copy IP Profile, in case anyone reading thinks it is).
As far as I can gather the IP Profile is held in (at least) two places in the BT Wholesale system. One is a database that holds the calculated figure and which the test reports, which in your case is 7.15, and the other I think is within the DSLAM itself, and that the update of that has failed.
There is some reset they were able to run or get BTW to run that sorted it. Whether it was a straight DLM reset or something else I don't know.
If you can get that through to EE I doubt, but!
However, although this would limit your maximum speed to the DSLAM(?) figure, it doesn't account in any way for the huge variations you describe. That seems to be typical of many EE connections we see complained about here, simply insufficient throughput capacity resulting in congestion. There are two solutions to that. Wait for them to upgrade it, (how likely is that now their sale to BT has been authorised?), and migration. If out of contracted minimum term.
The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - AAISP Home::1 80/20. Sync 59997/15142kbps @ 600m. - BQM