North-South divide in Lean Six Sigma Training ?

As a Lean Six Sigma trainer I have been traveling around the UK all year teaching Yellow, Green and Black belt classes.  I have noticed a large discrepancy in the number of people in classes from the South of England and the number from the North of England.  Classes in Leeds, Newcastle and Edinburgh have been averaging at 4 students ( with standard deviation of 1  ! ) compared to classes in Birmingham, London and Bristol that have been averaging 8 students ( with a standard deviation of 2 2).    The demographic in London classes is also different from that in classes in the North.  My observations also suggest that the average age for London based students is approx. 32 years ( with s.d. of approx 4 years ) whereas in the North the students are significantly older …my estimate is average of 40 ( with s.d. of approx 4 years ).
I have not yet had the time to do a detailed study  ( putting DMAIC to work ) so I am not going to jump  to conclusions,  however I am personally confident that the data would show statistically significance between North and South training class attendance if a study was made, data was collected and analysed.