The ambiguity here arises when an a/c is told told to intercept at a a certain altitude and report established this is not an instruction to decend on the g/p. An a/c must only decend when instructed either once established or after receiving the command "once established decend on the ILS" I know of a situation where a colleague of mine was told to report established at 4000ft, the a/c had been configured to decend once established, which it did. However this did not help when the controller realised that the a/c had left 4000ft with the glide against an opposite direction departure climbing to 3000ft. Technically a safe procedure, but in this instance not, owing to the pilot automatically assuming he was cleared to to decend once established. In my opinion a/c should not decend on the g/p without clearance to do so.