Hi Marlin, welcome to Say no to 0870.
This seems to be the case with most car dealerships. In many cases I have found that the conventional geographical number is available of from directory enquiries services such as
BT Phone Book. It is often the one which has been in service since the place opened as they don't seem to change them so as to force callers to phone the 084/087 non-geographical number (NGN). That's not to say that doesn't happen of course.
It is also commonplace to see a single dealership with different NGNs advertised in different places. This allows them to track what marketing is working.
In some cases the dealership is part of a chain and that company gives each one its own NGN and so too does the car manufacturer. Hence the dealer's own website might promote its NGN and the manufacturer's promotes another.
The dealerships and manufacturers are quite happy to allow the telephone companies to profiteer and some will be taking a cut themselves. They now have the choice of 03 numbers if they see it as a benefit to have call statistics, but they should pay for them.