For this British writer, who’s used to muddy, litter-strewn fields, pop-up tents from Aldi, and rowdy crowds of weekend warriors, Flow Festival was an entirely foreign – and welcome – experience. Set in an abandoned power plant in the heart of Helsinki, Finland, the metropolitan event has made a name for itself in the European festival roster with a line-up that skips between headline veterans and avant-garde performers. Pair its pioneering technology and impressive sustainability credentials with crowds of characteristically…