Thanks slick, I think I actualy get it now!
So it's just a matter of making sure I have the right hub adaptor thickness to make the wheel fit between the arch and all the gubbins on the inside....right?!

Ahh well, I've fired off an e-mail to some company that sells them, so hopefuly they can tell me for definate what I need to fit them.
Thanks for all the help guys.