Very good - thanks - only tiny nitpick is that Bates does not fit neatly with the other three for obvious reasons - Wisdom, Rockwell etc... are exactly the same

Hi Giggsy - thank you and yes, you're right. Originally the Bates group was actually of a slightly different type (although with the same keyword as the solution) and I changed it at the last minute for reasons I won't bore you with, but yes, in retrospect I agree the group is slightly less neat now!