BT issue any help appreciated.

[Inneeddofhelp]

Hi all,
The long and short of it is i have a BT 8mg package at home. Ive had a slow speed issue on and off since april. The current open fault with BT is dated from June 30th. Since then Ive had a new hub, 2 new master sockets, a new port at the exchange and a total rebuild of the line at the exchange. I stilll have the same issue, they line starts at a downstream rate of 6mg (ish) and at some point over the following 18-24 hours the service drops ( once or more) and I end up with a down stream rate of between 96k and 800k. Can anyone suggest a next step as im at a loss what to do next , who I can complain to apart from the service desk in India to get them to actually fix it? Is it worth switching provider or will I still be in the same situation?

Thanks for any suggestions.