Also you've got to weigh up the excess, customer service etc etc.
I think people also forget that a standard courtesy vehicle is all well and good but you've got to get your tank, possibly your RO, Di vessel etc etc out of your van and into the courtesy vehicle. And that's if you still have access to your vehicle and it's contents after a smash. For instance the back doors might be so smashed in you can't get you tank out or it could be holed. Poles and equipment could be damaged etc. If it's on the back of a lorry getting towed away, how are you going to get your tank out & home? I've had someone drive up the back of my Vivaro 8 years ago so I know what it's like. Luckily it wasn't too bad & I could still drive it home and get all my gear out and in to the courtesy van, then all back in a couple of weeks later.
We run two vans but personally I like the piece of mind of a courtesy wfp system & van on my drive within a day or so and all my tools covered. That's why it's currently Alexander Swan for me. It probably costs just an extra house or so a week extra in terms of extra money. Van insurance isn't a corner I want to cut.