The ladies would have to get to one of the main routes in order to travel comfortably and, as Rachel says, we don't know where in Sussex Norland is. According to Coaching Days & Coaching Ways by W. Outram Tristram, the trip from London to Exeter in 1773 with excellent horses, carriages and outriders to go ahead and bespeak lodgings and horses was about four days. Traveling without all the these luxuries would probably take longer as it would require stopping more frequently. I would guess four to six days for the trip from somewhere in Sussex to Exeter.