I took a photo of the original selector tower before removal. The new tower IS exactly in the same position, including the top section. I've thought that as an interim step, I COULD have connected the cables to the tower BEFORE inserting it to the gearbox. I could then have had someone shifting through the gears and I could have observed the corresponding movement in tower gear positions. I could still do this .... it's only held in place with two bolts ....... However, because I found that I could manually select all the gears and there was free movement to the disconnected gear lever, it could only be a fault with the cables .....
David