Courtesy car dispute

Good afternoon everyone!

My issue is that my Skoda Superb, our caravan tow car,  was involved in a minor accident, and has to be taken in for inspection by my insurers as a potential write off. I am insured with Swiftcover, which is part of the AXA group. In the meantime I am entitled to a courtesy car.

I decalred the car to be  modified, and stated it had been fitted with a Brink tow bar, professionally fitted. I have also paid the annual premium to have a courtesy car upgrade; this is the wording from the policy:

The optional temporary car we will provide you with in the event of a valid claim under Section A or B of this policy. The car provided will be of a similar size and transmission to your car and will have at least as many doors and seats as your car, up to a maximum of 7 seats.

However, the providers of the courtesy car say they cannot provide a car equipped to tow, and that they do not do so as their insurance does not cover it. To be fair, they were already doing badly when they said they were struggling to find me an estate car (this is Enterprise by the way.)

I can accept that the wording of the policy doesn't really cover this issue, and that perhaps I should have enquired about this when we bought our van earlier this year. I have raised this as a grievance with my insurers

So:

1. is this simply caveat emptor and more fool me for not checking, or are they being unreasonable?
2. does anyone use an insurance company where they know for a fact that a courtesy car will be an adequate tow car as a replacement? If so, please tell me who, as I am in the mood to change insurers.
3. how many of us haven't actually checked what we are entitled to?

Any thoughts welcome, and I hope this might save others the troubles I am going through :-)