The OS have still managed to produce the most consistently clear, accurate and usable mapping coverage of anywhere on the planet. You're right that they're not faultless, but they're about as good as it gets. We're very lucky, i reckon.
Yes that's right, they [OS maps] certainly have their faults but are still the best in the world, but the faults may explain the missing silbaby, it's one shapely mound [with the same angled slope as Silbury] for just dumped road material, I say try looking from midwinter until spring and you'll see it's form a lot better than in the summer [now would be the best time].