Necrothread reply:
Yes, the early missile was apparently considered for the Sea Dart role. I have only seen this mentioned once, however, IIRC in Butler.
It is not clear how this would have worked, given the disparity in range. Guidance would not be an issue, the same system could be cued by radar as it was in Darkfire, that part at least is very simple. But Sea Dart was intended to improve performance against faster strike aircraft and newer anti-ship missiles, especially in combination, so long range would seem to be a requirement if the goal is to prevent the missile launch.
If I find more I will post.