Summer dresses

[shitpark]

Not too tight, not too shapeless and baggy, not made of polyester, and under £50. I'm asking for too much it seems

And I don't want to reveal my knickers every time I bend down, or sit down. Where are they? I'm a. Size 8 - 10. Not that clothes sizing is accurate. I want to get dressed in the morning without having to think about it, literally have five minutes to achieve this.
All of last years summer clothes are shapeless rags. I'm totally fed up