Thanks folks, its looking less of a struggle all the time. I should have clarified the car part of it. I normally would have hired but have been offered the use of a car while in Philly so once I'm there life is easy! And I guess I could try and get one to 'return' but hiring is very much cheaper if I do it over here using one of the online companies and I don't think I'd be able to work out that kind of option.
Nick