My Dad worked for Granada and I can confirm that the vehicles were Viva estates (not vans). They were later replaced by Chevette estates. These also had opaque panels covering the rear side windows displaying the brand logo, but that's about all I remember about them, other than helping my Dad clean his up for the annual inspection which earned you a cool £100 bonus (a lot back then) if you had kept it in good order.
The Chevettes were replaced by Austin Metros (much to the distaste of most of the engineers) and Granada had attempted to make up for the lack of boot-space by building a kind of wooden underfloor "secret" storage area for components and small tools that partly occupied the spare-wheel well whilst raising the floor level of the useable boot-space. This was totally impractical in reality as you had to empty the boot first to lift the lid. Since vehicles emblazoned with TV rental logos had started to attract a lot of vehicle thefts and break-ins, the Metros abandoned the branded window panels and the Granada logo was instead embedded into an inch-wide white line running the length of the car and the engineers were issued with two magnetic strips which could be used to complete the white line and cover the logo so as to appear as an ordinary, not-so-appealing family car when you weren't at work.
