I have been noticing that my page has not always been loading too fast, so I have now installed the W3 Total Cache (W3TC) plugin for Wordpress. I'm hoping it has started to improve the performance of the site. I've been running some tests on the GTmetrix site http://gtmetrix.com/ and it looks like some improvements have been gained with this plugin - I have enabled some of the Apache modules that were shown as "disabled" in the plugin's control panel.