I've finally got it working!
I scrapped the demo layout I had made from Smiley's instructions, and rebuilt it from scratch, and it worked perfectly.
I can't think what could have been wrong with the previous one, but the important thing is that I have got it working.
Now I can get rid of the turning 'Y' and merge the rest of it into the layout I'm building.
Thanks Smileyman and everyone else.
Ian
