Cheers all, still working fingers crossed
Ash, funnily enough that's the one I used! thanks
The only thing I had to change for some reason is I had to loose the slashes that were escaping the dots in the address then it all worked.
These ones:
Options +FollowSymlinks
RewriteEngine OnRewriteCond %{HTTP_HOST} ^addondomain
\.co.uk [NC]
RewriteRule ^(.*) http://www.addondomain.co.uk/$1 [R=301,L]
RewriteCond %{HTTP_HOST} ^
www.addondomain.the-hosting-domain\.co.uk
RewriteRule ^(.*)$ http://www.addondomain.co.uk/$1 [R=permanent,L]
RewriteCond %{HTTP_HOST} ^addondomain.the-hosting-domain
\.co.uk
RewriteRule ^(.*)$ http://www.addondomain.co.uk/$1 [R=permanent,L]