Big problem here is people are becoming confused - the airlines determine the economic case and so far they have determined that they don't want to pay for Cat III. The high price of fuel may change their views though.
Also Bruce Byron does not have any bearing on what is installed - Airservices and the airport operators provide those services.
Anyone suggesting that GLS in CAT III conditions is just a hairsbreadth away is fooling themselves - fine to demonstrate it in VMC or a simulator but in the real live case there are many more considerations such as Runway Intrusion, Taxiway/Runway marking and lighting etc.
Even if the GLS equipped aircraft can land you have to quarantine the taxiways/runways from ground vehicles and other taxying aircraft.
In fact a simulator session can give a false sense of security as usually there is no "Taxying to the Gate" after the landing which can sometimes be extremely demanding.
If you think back the major accidents in low vis they have occurred not on Approach but on the ground because pilots/ATC were confused as to their ground position - eg Teneriffe.
Lighting and the upkeep of the lighting is the BIG cost. Facilities like the "no break generators" have to be brought into service before LVP operations can commence.
Here is a link to an ICAO powerpoint presentation: Aerodrome Operations in Limited Visibility Conditions which gives an idea of what is needed as visibility decreases.
www.icao.int/icao/en/anb/meetings/almaty/aerodrome_ops_limvis_en.pps