Thanks to all who sent replies.
Well I have gone from unhappy customer to a satisfied one.

Reason :- 2 different engineers arrived yesterday and the fitted up my second line, and they went into the loft so no boring through walls. These guys said they regurarly have to enter loft space to connect up and they called the original installers "a bunch of cowboys who give the rest of us a bad name".
As has been suggested the system now works fine with the second line installed.
However because of the problems I had I have posted a registered letter to Sky complaints department. I await the outcome in due course .