In reply to no_more_scotch_eggs:
England over-achieved in the 60s, Scotland over-achieved in the 70s, simple as that.
The normal order of things is that England will qualify but not get beyond the last 8, whilst the other home nations won't qualify. Occasionally you'll get anomalies, but in the end it comes down to the depth of your talent pool. Slovakia and Scotland have very similar populations, so the fact that there were level on points, with Slovakia edging it on GD, is no surprise.
Pleased to see Strachan hasn't lost his sense of humour though