"but I can't see any reason why they wouldn't have run Windows 7 quite well."
My 2GB Atom NC10 (which I only bought around 18 months ago from ebay for £45) ran Win 7 like shit. But with a recent upgrade to a 240Gb SSD and Win 10, it's now a perfectly usable machine, and is great for travelling. I too run Visual Studio on it for occasional airport lounge/ plane coding, although it's mainly for films and email. It's knocking on a bit so it's not the quickest, but the weight and battery life are good, and it does the job well enough for now.