re dates
August 2010 and 2011 they were a week apart (I was at both) because the way they follow the weekends in that month.

2012, 13, 14, there is effectively one less weekend and they get pushed together. Grove moves between the second and third weekend depending on this as it seems to be based on what day the month starts while Moira seems to be based on being the weekend before the Bank holiday
next one without a clash is 2015
i love both festivals

when it works out i can do Sidmouth Dartmoor Grove Moira and Towersey all in one month 8-)
regards cllr