clearing responses from many surveys?

Hi

I have copied the survey 126 times and changed the conditional rules. As the survey is critical i have tested each one twice and I'm happy that it's working as expected.

I now need to clear down all responses from all surveys, is there an easy way to do all in one go. Possibly i could do directly in the MySQL database, if so which tables & columns do i need to purge? I will off course back it all up before i start

Roy