Apologies but I'm fairly new to URL Rewrites. I've managed to get the rewrite working in the conventional sense but cannot force it to have a trailing slash.
Here is the code:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.html -f
RewriteRule ^(.*)$ /$1.html [L,QSA]