Either ring the service desk in India. Free call. I found them very helpful, others have sometimes found them less helpful. BT helpline: 0800 111 4567
Or try the mods at: http://bt.custhelp.com/app/contact_email/c/4951. But be aware they take 3 working days to reply: sometimes more if busy.
I hope you get somewhere with BT, but I believe that they don't give any guarantee on upload speeds, so you might find that they aren't very helpful (but I hope I'm wrong)!
Thanks sjtp and RichRolls - I have spoken with the call centre and got nowhere unfortunately. I have completed a form however and have been told an engineer visit will be required. Quick service indeed! Won't cost me will it? Another try and got 4.90 upload...!
I don't think there should be a cost, as they accepted a fault and it was them that decided to call out the engineer.
However, it is far from unknown for the various parts of BT service to get confused and to try to charge when they shouldn't. I hope this doesn't happen: if it does another round of discussions with the mods should get it sorted.