Varies from uni to uni, but it's pretty much a pass/fail sort of gig everywhere.
At Newcastle you can get Merit, Satisfactory, Borderline, or Unsatisfactory, with the first two being a pass and the latter two being a fail. The distinction between M/S and B/U are for the most part perfunctory, though obviously your ranking within your year does go some small way to supporting your F1 application.
The pass mark here waivers depending on the years overall performance, but there is no hard and fast ">2 standard deviations below must fail". If everyone in the year suddenly got 90% plus, everyone would pass.
The pass mark tends to fluctuate around the low 50s (%) from what i've seen so far.