Hi Dave,
I didn't have a problem with the adapter mounting to the wheels, however I did end up scrapping the idea and using 13" Cromodoras instead as the Calliper was too large for the original wheels.
The Aluminium adapter fitted the original steelies perfect and the threads worked fine with the original wheel bolts, I just couldn't get the wheels to turn past the calliper, even with 25mm worth of spacers!
Ended up selling them on ebay for a fraction of the cost I'd paid, but they were useless to me

This was during my trial and error phase, which actually hasn't stopped. My last silly acquisition was one of those 'Abarth' Fan case top covers - stupidly bought as it was much cheaper than they are going for on eBay. Only problem is that they have no mounting for the throttle linkage to connect to, so I have spent ages carving up the old cover and will now attempt a drill and rivet manoeuvre, all for a shiny aluminium lid in a filthy engine bay. The only advantage I can see is that it will free up the space that the old air box crudely takes up!