Probably because there wasn't one. I've NEVER seen a garage attached to the side of old farm houses, or even purpose built in the yards -I've known Bentley's to be kept outside along with Land rovers- and unless you've got it from the horse's mouth, how do you know that all the outbuildings were in use.
I was assuming that the outbuildings were used for the crops that were supplied----cattle-feed,borage,potatoes,rape etc,but not in all in the one place.
Daughter nearly bought a Bentley,but went for a Chrysler saloon instead--------cheaper.