Only one?... probably PFA, possibly Congo... but as I have a potato day less than a mile from my house next weekend I could get 20 different plants into the positions if I wanted :D..... I'd probably split so that I had 5 PFA, 5 Setanta, 5 Congo and 5 Lady Christl. Thankfully I'm not in that position, I will be growing lots of spuds this year cos I have a new plot to clear..
chrisc