I got a couple of sun visor courtesy lights and part loom from the scrappies a while back. Finished work early due to the bad weather so decided to mount the lamps and investigate the existing wiring loom hoping there may be connectors already taped up somewhere. No such luck. (Focus Style). However I did find a small red connector attached to the interior light loom. It is very similar to the connector for the visor courtesy lights but has 3 wires instead of 2. Like this one.. Would this be part of the security/entry system in higher spec models?

This is the auto light and rain sensor wire. I have recently retrofitted the sensor and can confirm that it worked without any fuses, extra wiring etc...
There may also be a similar connector but white plastic, this is for the auto dimming rear view mirror

Pretty sure it's for the internal alarm sensors as you suspect.

I didn't see a white plug. Only the red one. A bit annoying that they fit certain looms and not others. Oh well!. I will just have to get the soldering iron out and adapt the spare bit of loom I have.

If you are talking about the black connector in the picture then that's the auto rain/light sensor, white is the auto mirror, there is also a wire for the Bluetooth microphone ( I think that's also black from memory) but after re reading your post I don't recall a red plug anywhere :S

As far as I know the alarm system could be a possibility, also the Keyless Vehicle Module possibly too.

I'll have a look to see if I can find a wiring diagram

The plug in the picture is for the sun visor courtesy light. It's part of a spare loom I got with the lights. The red plug I found connected to the loom in my car is similar in shape and size but has 3 wires and not 2. Hope that helps.

Well this is the roof wiring in micro-cat

There are soo many which it could be from this list. I have no idea why ford would make so many variants

I agree. I can only try and work with what I have I suppose.