The seed potatos will often rot away and become horrible. I don't know what is going on this year with the spuds - my allotment neighbour has 2 entire plots over the spuds, and they aren't great and he has done nothing different this year to last. Mine are okay, but my volunteers, left from last year by accident are AMAZING! I wonder if the weather has anything to do with it. Mine were planted early, so benefited from that spring wet weather. Some places had late frosts, and if they were planted later, then it has been incredibly hot and dry. Sorry I can't be any help at all...............