I thought i would let you know the problem discovered by a BT engineer which appears to have solved my problems i have been suffering for eons.
Firstly i have quite an old large house and several years ago i got BT to move the telephone line from the rear of the house to the front as i moved my office. Instead of running a new line to the front of the house they installed a T junction and spurred off this to the front of the house. This created in effect two lines one of which was not being used to the rear and one to the front.Even though it was not used (in fact i didnt even know it was there) it was drastically reducing the signal on my Broadband as soon as the engineer disconnected this unused line my speed doubled, i have now since last Friday achieved the most consistant speeds i have ever had not going below 2MB and my profile is currently 6MB so i expect this possibly to rise.I was getting at times 256k
So this may be of help to any of you who have older properties because who knows what BT has done to wiring over the years.It may be worth checking you havent got any old wiring running from your line as i had.