Just re-read my original post and after a few weeks use, I can comment again.
I found the biggest difference to the performance was the wall connection for the BT hub i.e. where the telephone/broadband filter connects to BT. We regularly have corrosion on the contacts here and a new BT Homereach master socket worked wonders.
No trouble at all now, except drop-outs in real time - I need a new aerial!
