Thanks all. I've been quite busy at work. I've been implementing this on some other sites. It's more that just adding code snippets. Some code needs to be removed (or commented out) and it is different for every site. Plus some other options and settings need to be correct too.
If you would like me to customize it for your site, shoot PM me.
Added an 'Upgrade My Membership' link just under the top links. Will only will show to logged in members who are not in any of the supporting member usergroups.