<<To pick up on one of your earlier points, all landings below Cat 1 minima are reported to the CAA,>>
OK BizJetJock, perhaps you can tell me how it's done. Having worked as a Heathrow controller most of my life I have to say that I was not aware such action was taken. Just the number of Cat II and Cat III landings which take place at Heathrow and other large airports during bad weather suggests that the paperwork involved would be mountainous.
With the usual proviso that things might have changed since I retired, I am not aware of any ATC involvement in such arrangements - we would have been too busy! At this time of the year Heathrow is below Cat 1 quite frequently and hundreds upon hundreds of flights operate below Cat 1.