thanks for all the replies. I looked through the UK CAA documents. Also ICAO doc 9432 ( I think it was).
The ICAO didn't really give me an answer.
the last situation where I experienced this
Full procedure ILS RWY 27 in India. We were about 4 miles from turning inbound. ATC cleared us the ILS APP and used the words "report established."
NOT "report established ILS" Or "report established LOC". Just "report established"
I know thatat my homebase "report established" means established on localizer. But just "report established" doesn't seems correct to me as it is open to interpretation.
It is really not a safety related question. This is just to satisfy my curiousity.