Suz - Thanks and great to hear from you! We do have Zara here. I think that dress is too hot for me - I'm more after light short sleeves - and also completely not needing ironing (I just don't iron on holidays, especially camping ones - but even in a recent trip to the UK where we stayed in rooms, I was too exhausted to do it, even if I had got hold of an iron). I can easily check Zara out though - there's one near my workplace.
Sal - thanks. I hadn't come across Humidity but they have some delightful styles.. Not sure about the non wrinkle side though - I short of presume that 100% cotton would need ironing. I have loved that white dress of yours since you bought it - and in fact until recently had a quite similar one that I'd worn for 10+ years (bought from Ezibuy ironically) I can't work out if culled it (would have only been for staining reasons) or if it just got lost in the house move.
Angie - Thanks! Boden is probably the one place I would risk ordering from. There's one dress that nearly meets my requirements (if wrinkle free)
Joy - all your requirements sound difficult and I feel you. I'm not fan of V necks on myself either - not a great look with a small bust. I'll check out swim dresses
Jules - thanks for chiming in. Hard to express what our heat is like! I probably wouldn't even be outside at the hottest Australian temps, but I was surprised how hot the UK was in summer (and also Tasmania, where I recently holidayed)