If you want something that works in actual warm conditions, check out the Rab Boreas – it’s not very windproof, or very water resistant, but it’s oddly brilliant on days when you want something a little more than a baselayer tee, but without getting hot and sweaty – £60-ish, but not very protective.
Or, if you want something a bit more protective, but still quite breathable, the VR Flex is ace. Not completely windproof, but the pay-off is better breathability plus the side panels are more breathable again stretch fabric. Around £100 but good.
I wouldn’t touch either PowerShield or Windstopper for summer use unless you run really cool. What you really want is some sort of non-membrane, double weave fabric. The North Face summer soft shell – really, that’s it’s name – is pretty good along those lines.
Big picture: it’s always a balance between weather protection and breathability/comfort.