I used WBAC once. Very satisfied. Completely hassle free.
It wasn't worth much. It was 16 years old and was badly rusted. Although it had passed its MOT it had a list of advisories as long as your arm. WBAC gave me £300-odd.
Just drove it about a mile or so down there, offered them the service history (they only wanted the MoT) signed a couple of forms and walked home. Easy peasy and the money was in my account when I got home
Now I'm sure that if I had some knowledge about cars and some experience of how to sell them (I have absolutely none of either, nor do I have any interest in learning) I could have got more. But as it was a terrible heap I doubt I could have got a huge lot more.