] John urges Catherine to make ready for a carriage ride to Claverton Down...

Did you notice that when they talked about the drive in chapter 7, John said 'I will drive you up Lansdown Hill tomorrow.' Then in chapter 9 he said 'We are going up Claverton Down.' That's two different places!:)
Claverton Down, to the south-east of bath, is in the opposite direction to John Thorpe's actual project of the previous day, Lansdowne-hill. [NA notes]