There is a rumour (and it is only a rumour) that when the procedure includes an APS or APP unit which will 'filter' traffic so only one aircraft is using it at a time, the CAA might allow it. I believe this is why they have approved the ILS procedure at Walney Island (a FISO unit) ie because Warton ATC only allows one aircraft in the procedure at a time and will hold succeeding aircraft off until the first one has either landed or gone around.