Eddie, sorry but you're wrong. Unless there is a planning condition, the garage can be used as part of the main house without further permission. If there is a condition restricting the use to vehicle storage only, or if they have converted it to a separate unit, then planning permission would be required. If the garage has not been converted and they are just living in it, they may well be assessed as having no proper home if they were applying for Council Housing. A bit more background might help us reach a useful answer for you.