Sabenaboy,
Also, when you clear traffic for the ils when he's LOC established, what's stopping him to not to think he might be allowed to descent immediately to the published alt?
But that isn't the clearance. The clearance given is to 'descend on the glidepath'.
How about....
"......when established, descend on the glidepath, QNH..."
.....which is current UK phraseology.