Well, happy to say, I finally made it to the roof !!
I decided to search every screen very
slowly and in doing so discovered I had been constantly missing one of the "angled" arrows.
Once I included that
in the route, I got to the roof without any problems
Anyway, thanks for the help. You have all been most kind
And a special thanks to you
, of course, Rushes, for sending me the saved game. [Even though I won't need to use it now.]
Plus, there is more good news in that I have at last found
the saved games !! After fruitlessly searching the whole of C Drive for them I eventually found them in D Drive.
[Grrrrr. Windows 7 Frustrations !!!!