It's amusing how many instructors don't actually know what the current rules are and what they will be in the future. Myself included.
The problem is the UK has some oddities. Everywhere else in EASA land to teach IR you must be an IRI. It's only when you start throwing the IMCr into pot that the waters become muddied.
If my reading of Part FCL is correct an IRI is still going to be needed for IR.