Any Vehicle that is subject to a O’licence must be kept at the registered address stated on the O’licence as its registered base when not out working!
If a vehicle is parked up outside this guys house then its a good guess that it isnt the registered base! So he will be braking the terms of his/her O’Licence!
If it bothers you or your neighbours then contact the area TC office and inform them that this is happining! you will find it will stop soon after!