Translation folders unpack with incorrect permissions

I have downloaded and expanded a translation (Welsh) and discovered that it will not install correctly because each folder is unpacked with unhelpful permission settings. Under OSX, they are reported as staff:Custom and everyone:No Access.

If I set everyone:Read Only for a sample of folders — in this case the theme translation folders — then that part of the code / install runs ok, but of course, there are dozens of folders with unhelpful permissions set, through the code-base.

Does anyone know if there is a way to set all the folder permissions appropriately? Perhaps by expanding the translation separately, changing the permissions wholesale and then repackaging for un-packaging within the drupal code? is there an open source utility that would allow this?

Thanks for any assistance...