Well, this was not as straight-forward as i first thought. Why? Because the timer job does not run in the same App Domain as the web application. They are in two separate processes : W3WP.EXE and OWSTIMER.EXE for the Web Application worker process and the SharePoint timer respectively.
So, how do you go about it?
Well, firstly you need to add reference to your timer job as follows (unless your using VB !):
using (SPSite site = new SPSite(“http://SiteCollectionUrl"))
Configuration config = WebConfigurationManager.OpenWebConfiguration(“/”, site.WebApplication.Name);
Admittedly, this solution is hard coding the Uri of the Site Collection, but this is purely for demonstration purposes.