I have to agree with you on the fact that the later Saxons did have a form of Law (why,even Wikipedia says that), but to then point out that Common law, which is the basis of British law even to this day, only emerged in the Norman period. Everything prior (i'm talking about Law here) really did not matter to such great extent, only that some parts of it were assumed into the Norman law code.
Also, I wouldn't say to any degree that England at this time was a civilized place. Yes, Alfred and his son unified the land, but it was still a back water, barbarous place. Edward the Confessor can be seen as a truely civilized king to large extent, but it again must be noted the norman influence upon his court.
Sorry, but I disagree. England was a popular target for invasion because it was prosperous, peaceful and rich.