About three years ago I spent some time at the Belgrano on an aerodrome safeguarding course. There was talk then of explicity prohibiting unofficial IAPs. They haven't done it yet so maybe it isn't easy but I'm with Keef. It if all went horribly wrong then they would find some means to prosecute (and rightly so in my view.)
Certain companies do have their own IAPs at individual airfields approved by CAA, and not requiring full ATC. But don't hang your hat on the recent consultation paper which mentioned IAPs at non-ATC airfields. It went on to say they would be considered if accompanied by a 'robust safety case'. They would mean robust.
VA