As for Will's list, I am quite sure that most international tourists have never heard of Morris dancing. The same applies even to musicians.

If I were to organize a weekend trip to London for mass tourists, and it had to include a concert, a Britpop band would be the safest choice. Nevertheless, "special interest" tours with English folk music can be successful: make a good mixture of authenticity and fun; explain the jokes in slow and clear English if necessary.