APP rules
I did an Aussie IR first where the rules were explicit - you can not join an instrument approach after the published IAF. There may be an IAF indicated at or near the CF. You can manouver as required above the MSA inorder ot intercept the required course at the IAF (by <30deg). Also no IFR approaches allowed below MSA where no published procedure exists (regardless of accuracy).
I have never found any explicit advice in the JAA regs but maybe I didn't look hard enough. Perhaps this means that the default is the ICAO published rules, but who has the energy to read these as well.
Perhaps posting this topic in the Instructor forum would generate more replies from the legal perespective.