Moving to root needs tidy up

I used the advice of my host (Heart) to move my site from (site)/blog to root (site). It works except that the media links are not working, and the permalinks still all refer to (site)/blog.
The WordPress address is root (site) but the Site address URL is still (site)/blog

The htaccess file shows:

DirectoryIndex index.php
RewriteEngine off
SetEnv DEFAULT_PHP_VERSION 5
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blog/
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

That first line was put in by Heart to get it working!
I think perhaps I should have set the site address as (site) before I moved the site files (if I read the Codex right).
I have the plugin Better Search Replace ready to use, but I’m reluctant at present.

Please can I have some advice!!
Thanks