They are rip off merchants...they prey on those who are desperate for cash, and that's the majority of people who enquire seriously with them.
They sell the vehicles then on to the trade, and make sometimes a lot of profit on certain vehicles - which is fair enough and how it goes.
But they always try to find faults with the vehicles, sometimes they pick up on ridiculous things, like the depth of the paint.
I've experienced it first hand, they 'annoyed' me somewhat so I enquired as to the value of 'RX56 UJN' (I'll leave someone to find out what vehicle that is)

I then took said vehicle to them, to see how they would try and knock the price down...they didn't know what to do or say really with this vehicle. Most of the 'experts' who work there know nothing, it was fun telling them all about the car and them not understanding what I was saying.
A good friends sister wanted to sell her car, but 'didn't want to trouble me' with asking to sell it for her etc. So she took it along to webuyanycar and accepted their offer of £240. When she told me I was angry, not at her but at them. So I tracked down the vehicle, bought it from auction for £750 then sold it for £1275 and gave her the profit; it taught her to be more careful. This illustrates the need to even spend a few minutes researching. Book prices are useless, I know only one trader who uses them, and he's a moron. The most important figure is 'realistic retail price' which CAP are sometimes good at getting near to. Book prices are only indicitive, actual listed prices of similiar vehicles on ebay and autotrader give the best results, sometimes this will be higher or lower than book price...and no matter what you use as a guide, webuyanycar will offer you considerably less.
So, no matter what...please never let anyone you know go to webuyanycar!