Where can I buy pictures or paintings of London?

I've always had this passionate fascination with Europe, particularly London. I'm redoing my room and want to include classic paintings/pictures of London and other places in Europe. Maybe paintings of Big Ben, double decker buses, opera houses, or the classic red telephone booth. I want a very sophisticated look to the pictures and not just some picture someone snapped on their iphones. Does anyone know a website or place where I can find these?Also, what other London-type, vintage influences can I include other than the pictures? I have a beautiful wall mirror that is black and white Paris themed. It has a stunning painting of a fashion woman in a sort of perfume ad. Other ideas/advice? Thanks!!!