Killed site trying to move from subdomain to root

I’ve installed wp on a root domain of an existing site.
When I was ready to move it, I copied the old site files into a folder (old site) at the root and used cPanel to copy all the files from the subdirectory installation to public_html.
Seemed like a good idea… except I accidently Moved rather than copied the files, and they ended up in a folder (named the same as the subdomain) located in the (old site) folder.
At the time of moving there were a couple of error messages saying “couldn’t move file, already exists”: I didn’t record them though.

Naturally at this point the site is no longer accessable at the subdomain.

No problem, I thought I’ll just copy the files back to preserve my original subdomain installation.
No luck: a 403 server error:

Forbidden

You don’t have permission to access / on this server.

Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.

I’d also tried copying it from the (old site) subfolder into the root, which worked, but the site still didn’t work: actually it produced an unformatted site with some images and text and background colour but no CSS) for a little while (at both the main domain and subdomain): I’m guessing till the cache cleared.

I’m guessing I’ve lost a critical file like ht.access or wp-config or something: but I can’t see anything missing.

These are the files present in the subdomain. (The folders have 755 permissions and the files 644)

Name
cgi-bin
wp-admin
wp-content
wp-includes
.htaccess
error_log
index.php
license.txt
readme.html
robots.txt
wp-activate.php
wp-app.php
wp-atom.php
wp-blog-header.php
wp-comments-post.php
wp-commentsrss2.php
wp-config-sample.php
wp-config.php
wp-cron.php
wp-feed.php
wp-links-opml.php
wp-load.php
wp-login.php
wp-mail.php
wp-pass.php
wp-rdf.php
wp-register.php
wp-rss.php
wp-rss2.php
wp-settings.php
wp-signup.php
wp-trackback.php
xmlrpc.php

Any ideas greatly appreciated.
I’m guessing if I can’t figure out what to replace, I will need to reinstall wordpress and hook it up to the database again (which I’m thinking should be totally unaffected [gulp])