Thanks for that. I had looked at that page and I have done everything up to the MythTV part. Controlling an A/C (as in Air-conditioning, not a typo of A/V) through MythTV wasn't that useful for me.
I'm actually wanting to create an IR Climate device and that's where I run into difficulties. From my understanding (which is a bit vague at the moment, I'm new to this) I need an interface device (the IR transmitter) to control IR equipment, but I can't set the mceusb2 device up as an interface yet.
So I'm wondering if there was a way of setting up a generic interface that runs scripts for the commands (like you've done in MythTV for the channel changing), but so that it will work in LMCE for general control and responding to events.