** when i first moved in, and ADSL was installed by BT, the engineer with his tester managed a SYNC at 2meg, my router got 1.5 give or take, when the engineer came two/three months back, his synced at around 1meg which was inline with my router at around 900k. All testing has been done my the master socket. From there I have a new BT ADSL Faceplate with a RJ45 connection and Cat 6 to the ADSL Router, The engineer also tested from there and also get exactly the same Sync Speed + the Cat 6 has been fully tested, so I know internally all is ok
How long is the cat6 to the router, with these sort of line stats you really want it as close as possible to the NTE and take a lot of care over filtering. You mention BT ADSL faceplate, I assume this is a filtered one and that the extension wiring is run from the filtered side, if that assumption is incorrect that would be worth trying.
Is the bell wire connected? If so, disconnecting this may help. http://www.kitz.co.uk/adsl/socket.htm
If I read the thread correctly someone mentioned Be is available on your exchange, you might possibly do better with their exchange equipment/backhaul than BT's. Probably worth looking at AAISP who have better-than-average BT-wrangling skills and also do lines running over Be - they have a bit of a reputation for being expensive but on a long lower-speed line with mostly-evening use, especially if with Be, you're unlikely to have a problem racking up a huge bill
They also have line bonding which, while more expensive than a single line, is not double the cost (if you do want to look at bonding, you'll need a second phone line to run it over so you might like to note that post office 'home phone' often have cheap deals on voice line installation).
BT assure me its not a line fault(even though I do still get crossed lines).
If you haven't specifically reported crossed lines as a voice fault I think you should do so.