c. Pass a ME IR(A) Skill Test with a UK CAA Staff Flight Examiner.
And the Skill Test for the upgrade from SE IR(A) is (or at least was when I did it in 2004) a much shorter test involving just 2 approaches and a circle to land. The CAA fee is the same though.
Since the ME IR(A) course is 5 hours longer, there is in effect no extra training overhead in getting the SE IR(A) first, just the test and issues fees to think about.