I have a maximum download (connection) speed of 3.5MB at my exchange which is a Local Loop Unbundling or LLU from which I live about 5km as the crow files.
My expected maximum will be only 70% of this at about 2.5MB due to signal to noise ratio loss on the BT line, dont bother trying to change your MTU or any TCP tweak settings you will probably cause more problems with the speed becoming lower maybe even cutting yourself off your own broadband connection
However most ISP use Local Loop Unbundling is the process by which third party networkoperators are able to install equipment in to BT telephone exchanges in order to provide their own services without having to touch BT's network. Only the copper pair from the exchange to the premises, which remains the property of BT, is used by the third party
. Use SamKnowsBest
to check what options you have at your local BT exchange BT copper line MAX is only 8MB irrespective of the the LLU that you use this means your ISP hardware.
Optical Cables MAX is 20MB and only Virgin Media in the UK can use this transmission medium.
I used to get only 750kbps which is not even 1MB now I can get double that between about 1500kbps - 1800kbps which is still only 1.8MB depending upon the time of day.
Also make sure that your connection is not shared with another user they will steal your bandwidth ensure that if you are using wireless use a WEP or even better a WPA-PSK encryption. Close all instances of P2P or FTP uploading during the speed test.http://www.speed.io/index_en.html
My Results as a comparisionhttp://speed.io/backend/result/24801225?pID=project1
There is not a lot you can do other than report this slow speed to this website the more they can build up a picture of the bad or NOT SPOT areas then your ISP will have to act to ensure that you don't move your service to another provider.http://www.broadband-notspot.org.uk/NOTE:
If you have the same problem as me then unless you can get Virgin Media Cable that can supply upto 20MB download speeds then BT maximum 8MB speed will be your limit expect to get about 4MB using the BT copper wired pair and your ISP's own router if you live over 5 miles from the exchange.