That's their game plan, competive quite online then you go to one of their centres and all of a sudden now they have seen your car in the flesh it's worth a lot less than they quoted
I'm not defending them, but how many people describe a car as mint and it's actually got loads of marks on it.
If you are completely honest with every mark/dent/scratch they would not knock you down on price because it's as described.
And again, my point - If they do you can just walk away!?
It happened to me when I buying a GTI ... went to one car advertised on the forum as in good condition and it was genuinely one of the worst condition cars I've ever seen. Had not even been washed let alone cleaned in the last 25 years.