Expert only, Firefox only, only if you know what you're doing. USE AT YOUR OWN RISK

1. Install Greasemonkey from http://www.greasespot.net/ (you'll have to click the Allowed sites button at the top of the screen and allow the site, then click the link again when you click install) FAQ
2. Click this link to install the script (if the install window doesn't come up, but it takes you to the file itself, go to Tools -> Greasemonkey -> Install script) don't click the "Install" button at the top of the page, it doesn't work
3. A small window should appear with an Install button. Click Install.
4. The next time you go to a page on the Warwick website you'll be asked for the calendar page that you want to add to. You will only be asked once - if you want to change it or if you get it wrong, you'll have to go to Tools -> Greasemonkey -> Manage scripts then click Uninstall with the "Also remove configuration settings" checkbox checked
5. The script will now be active (there'll be a little monkey in the bottom right hand corner telling you that Greasemonkey is active). When you go to calendar pages and click on events, you should now get an extra link:
   
6. Click the link, and you'll be taken to a create page with all the links filled in.

This link works with the hCal format, so it would be possible to adapt it for any website on the Internet that has hCal (you'd have to add it to the list of allowed sites). There may be a limitation in that it looks for a table and adds the link in a final extra row (it should really just insert a div at the end of the vevent div, but hey ho)