Locales - New locales not copying assets across
Solved - What was needed was to use the Update Asset Indexes tool in the settings of craft. If I do this just after creating a new Locale, before doing anything else, when my articles are created they know where to look for their assets. So relieved

Also noticed that to get a matrix to copy across locales (as well as setting the matrix field to NOT TRANSLATABLE and the fields within the matrix to TRANSLATABLE) it was necessary to do a slight change to the original matrix after creating a new asset (such as adding a space after the title). This forced the matrix to copy across. 

Hope this helps someone else