This is why we here are in danger of getting into a right pickle by not being really pedantic and precise about terms, because IPv6 + TCP + timestamps TCP payload rate is not the same at all as sync rate or IP profile or clueless.aa.net.uk’s tx-rate.
And adverts for ‘speed’ are absolutely hopeless because they never say what stuff it is the speed of.
ISPs need to be absolutely clear whether they are talking about sync rates or what. Sync rates are probably the best, because they are well defined. But they are not very helpful to the user as they need to be down-converted into something usable and so they are misleading. If you any of you are still on ADSL2+ or lower then the ATM efficiency of a mere 88.44% [in one typical case] is not good (that is, IP PDU rate = 0.8844 * sync rate ). If you are on FTTC then that efficiency figure is far, far better at a typical 96.69% IP PDU rate / sync rate [G.INP on, but on low setting], Kitz' figure. But in both cases you will always have to take off another big chunk if you are switching to talking about TCP payload rates (as in the true time to download a file, straight).
And speed testers are absolutely all over the place. You simply cannot trust them. If the whole network is really quiet then of course you can believe the results of a download of the thinkbroadband test download files. (Thinkbroadband has a speedtester, but I am not talking about that.)
Whenever you are doing any of these speed tests you need to check for alien traffic initiated by boxes in your own network. No one has mentioned this. AA users can do a traffic capture, triggered by a button in clueless, if unsure.
You also nee to check that you are not under attack. I took a look at the attacks I received over a 10 s period, from Russia, China, Italy, Ireland and the US. It was not a great amount of traffic, up it is there. Another thing that a traffic capture will sort out.
AA staff should be checking this for you, not just telling you to go away. And they should be helping customers to get deconfused about the various numbers.
After you have checked your numbers, give RevK an email if customer service are being dismissive, or tell customer service to copy your email to him.