Hi Elaine, I am not sure if you want a static caravan or if you are towing, but the Wild Rose caravan site at Ormside near Appleby in Cumbria has excellent views, particularly where the static caravans are, of the Settle & Carlisle line, some areas of the site are better than others.
That being said the S&C does not have a great deal of freight compared to some main lines, between 3 and 5 scheduled freight a day depending on the day and during daylight, with the occasional unscheduled one, but you should be able to catch at least one or two charter trains each week, including steam.