Thank you for your interest gentleman, and I can now declare that (after the FIFTH engineers' visit) I am (once again) connected!!!
I would have hugged the engineers, but at least one of them had rather pronounced BO! I have had three, yes three, pairs of boots climbing up and down my stairs all day.
For the technically minded, the problem was in the 'cab' - I was put onto port 51, 52 or 53, depending on which of the 5 sets of engineers' visits we are talking about. It was a '50 port card', so I was on a new card. And the card proved to be faulty. No other household had used it, and no one until today had thought of testing it...Errgggh
I am getting 33.96megs download, 7.68 megs upload. And my new best friends say that may improve a little over coming days as my 'profile' settles down. A bit like my blood pressure.