How do I alter htaccess to change htm to html ?

I've finally upgraded my site from Evo to Rev 2.2.4 and all going well so far.

However, on previous site all files had the file ext .htm and now Rev puts them in .html

I've tried two methods;

first - in Rev manager in /system/content types - changed extension there, cleared cache etc and the pages don't work either with .htm or .html !!!!

second - in htaccess i've added a line;

RewriteRule ^(.*)\.htm$ $1.html [R=permanent]

so my htaccess looks like this;

# Friendly URLs Part
RewriteEngine On
RewriteBase /
RewriteRule ^(.*)\.htm$ $1.html [R=permanent]
RewriteCond %{HTTP_HOST} .
# Force all pages to go to www.domain.com for SEO
RewriteCond %{HTTP_HOST} !^www\.djcdesign\.co.uk [NC]
RewriteRule (.*) http://www.djcdesign.co.uk/$1 [R=301,L]
# Friendly URLs
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]
# Additional Settings Follow
ExpiresActive On
ExpiresByType image/gif A2592000
ExpiresByType image/jpeg A2592000
ExpiresByType image/png A2592000
BrowserMatch "MSIE" brokenvary=1
BrowserMatch "Mozilla/4.[0-9]{2}" brokenvary=1
BrowserMatch "Opera" !brokenvary
SetEnvIf brokenvary 1 force-no-vary

But doesn't seem to do anything - .htm files still cause an error

Any ideas - as i guess my SEO is going to be effected big time !

Thanks, David

On my host, I had to change:

RewriteRule ^(.*)\.htm$ $1.html [R=permanent]

to:

RewriteRule ^(.*).htm$ $1.html [R=permanent]

For some reason, the \. was not registering correctly (although this is standard)