Blog Default causing errors in admin area

I've got a problem with new site creation when using the blog templates plugin.

Firstly, the CSS for the dashboard is attempting to load from a path with an extra "/" in it (see screenshot) so i get a pretty nasty looking admin area

Secondly, when i click in the admin bar to visit the site the url is structured like this mydomain.net/blogdefault/mysubsite which visits the default blog and not the new one and gives a 404 error

Finally if i try to edit a page/post then i get the standard WP "You are not allowed to edit this item." error message as one again "/blogdefault/" appears in the url (this url also has the extra "/" in it too)