I have gone over everything again and it is now joined up. I have saved as .STL and am sending a test piece off to the print company for their comments.

Thanks!

Gordon

Just a thought
You can try not joining your parts and export the stl file with all of the components , I find that if they are touching or intersecting each other it should print.
I find unioning parts sometimes generates errors
Also Un unioned models are easy to change later if there any problem parts
cheers
shayne