Therefore something somewhere is either lying to us, is misinformed or is confused. But whatever else, downloads we do the same each week which used to take 30s now take 50s, regardless of time of day. This is commensurate with a useable level of 18 and not ~30 meg.
It may or may not be related to your problem but about a month ago speedtest.net was saying my download speed was only 23Mbps rather than the usual 38Mbps.
I went round the whole check the connections, recycle modems, routers but no matter what I tried I got 23Mbps.
A little bit later I was on another machine in my house, a rather smaller HP Microserver and I got the usual 38Mbps. Thinking whatever had been the problem had resolved itself I tried again on my main server - 23Mbps. Seemed to point at my main server as being the problem, network card failing or something.
I tried a different browser, Chrome and got 38Mbps, IE9 was 38Mbps, FF10 (I think) 23Mbps. So a problem with FF on one particular machine. Deleted and reinstalled FF and straight back up to 38Mbps where it has remained ever since.
No idea exactly what the problem with FF was, but it was indeed a FF problem - nothing to do with my connection at all.