Hi,
You've raised a query I had about mounting filters, Circular Polarising & NDs to the RX100, but it seems my question has been answered now, however as I live in the UK no one stocks Carryspeed or the glue-on Lensmate, so if I do buy a Sony RX I'll have to see what I can rig up or adapt somehow to fit & work.
Thanks for the info, it will help me decide which camera I hope to get.