Creating a view block inside a fieldset using templates
Put the template file in your themes directory not views theme directory. It will detect it there. I like to have a views directory inside the themes template directory to organize view template files. I mimic views naming convention for a directory structure so views-view-fields--brands--default.tpl.php and views-view-grid--brands--default.tpl.php would go in:

views/brands/default

It's a nice way to keep the files organized.