The Piccolo ones from M&S, the ones from Portugal, have been very good lately and the ones from Sainsbury's, grown in the Netherlands, have been quite good too. I should have mentioned that the originator of this recipe, Rachel Roddy (though it's a traditional Italian dish), suggests cutting up the tomatoes first. That way the bits of skin in the sauce aren't as big. That doesn't bother me one way or the other but I thought I'd mention it. If the toms aren't quite up to snuff the addition of the small amount of sugar makes a miraculous difference. Many Italian cooks do that even in the height of summer when the tomatoes are at their best. You could always use your favourite tinned toms. The sugar is an automatic addition to any tomato-based sauce I ever make.