The OS Explorer maps are, quite simply, excellent maps. The clarity and detail is second to none, and the balance between size and coverage is spot on. We use them to plan cycle routes suitable for small children and I know of no better map for this purpose.
Comments that the map is "too big" miss the point - the size (and the amount of information this allows to be packed in) is its strength. If you need a smaller map, or a map to use in a car, you probably want to look elsewhere. But if you want the detail, then it's all here.