I don't actually have an aftermarket alarm, just the one that came from the factory - and I'm not sure it even works!.

I'd prefer not to have a remote fob on the keyring (silly, I know!) so would like to use a standard Ford remote key.

If the key could be programmed to an alarm I don't mind going down that route, but thought a Ford remote control spliced into the lock circuits might be easier/cheaper/neater/quicker.