53 Summerhill Parade is for sale and rent collector Peter Byrne will soon be looking for a new job.   Under one collapsing roof in Dublin's North Inner City, Peter plays host to a potted demographic of modern Irish society, all of whom must soon move on.   The tumbledown house is a picture of displacement; one room is home to an Iranian dissident, another to an entire family of Roma, another to a plumber from Poland.  And as a former farmer, Peter is as much a foreigner in Dublin as his residents.  Move On reveals an unsettled and unforgiving environment in which permanence is alien.