
I sold a pup to a lovely family in Belfast (Im near Portsmouth), they did a round trip non stop (poor them!). The pup wasnt phased by the journey at all, she slept through most of it, had toilet stops on newspaper, had bites to eat and slept again.
At the other end apparently she was bounding about like she owned the place!
I wouldnt be overly concerned, especially if the woman has bought from London before. Im sure your pup wont mind traveling one bit. If shes the ideal home, and the woman knows whats needed for a long journey, then I wouldnt have a problem JMO :)