Ok, I understand that, but I suggest that you make a proposal or post on the OSM forums explaining why all the refs should be changed, as there may be users and data consumers that are used to and rely on the existing refs for their workflow or software. Relations like (https://www.openstreetmap.org/relation/102788) have used ref=Piccadilly since 2009, so I don't think it's appropriate to change it without first discussing with the wider community. If you wanted to add these 3 letter codes as official_ref instead, that shouldn't cause any problems for anyone. Thanks.