After having spent eighteen months trying to get the time to work on a Panels-based Drupal theme, I've finally accepted it isn't going to happen. I need to concentrate more on improving the site and adding functionality. I also want to enjoy the benefits of some of the work we've been doing recently with Display Suite, an alternative, and more lightweight, display engine.
To that end, I've switched back to Drupal's default Garland theme, which I will augment incrementally as and when I need to. This should hopefully mean I can get improvements onto this website sooner rather than later.