Hi Everyone who has kindly helped with this one, I now have a nice pair of complete swing arms hubs and drums ready to go on the body as soon as its back from the bodyshop ( when I've finally decided on a colour, but thats something no one can help me with!)
Basically I think it was solved by a number of things;
Removal of excessive paint on the 'stubs' the shoes pivot on
Filing of the edges of the pressings of the handbrake levers.
The second manufacturers shoes seemed to be a better fit (even though with a vernier the differences were minimal)
The auto adjusters had to be unbelievably tight to the shoes wall.
centering had to be mm perfect.
I think I was unlucky in that all components were just to the tolerance limit and when they errors added up nothing was going to fit.
Once again many thanks, now back to the mystery of italian paint codes