Thanks guys for the update.
I’ve been trying to get the standard hot linking code to work, but to no avail. It keeps blocking all access to the images, even from the websites that are whitelisted (including the WP site which hosts the images). My server does not have Lightspeed, but it does run with DSO for caching so I am assuming that this is also not compatible with the code? Maybe worth mentioning this in the troubleshooting info. The ‘dumbed down’ version of the hot-linking code seems to work just fine though!
Cheers, James