Re: Would there have been seven seasons if there were no Seven?
yes and no
I think Sevens arrival also brough the doctor to life and the two of them worked very well together and improved each others characters while the rest of the crew stagnated - season 6 and 7 essentially became the Seven and the doctor show with a few bones throw to the other characters here and there (with some good results and some bad)
I think Seven and the doctor saved the show (she was the catalyst for that so i guess you could argue she saved the show)
Go to London, I guarantee you'll either be mugged or not appreciated. Catch the train to London, stopping at Rejection, Disappointment, Backstabbing Central and Shattered Dreams Parkway