Personally I feel some of these threads can literally be quite dangerous, I'm not suggesting people would launch off into weather as authorised by PPRuNe (or would they) but theres now a new rumour floating about that SPIR minima is 531.35 meters (or whatever) due to some wonderful manipulation of a pocket calculator and some CATII landing lights.
I think that you have mis-read the posts.
No one is suggesting that a single pilot can use and RVR or CMV minima of less than 800m without Autopilot etc.
What people have quite correctly pointed out is that when RVR is not reported, a
visibility of 533m will when the appropriate lighting is available and the appropriate EU-OPS factor is applied give a CMV of 800m.
There is absolutely nothing wrong with that an it is 100% in compliance with UK and European requirements.
When describing the absolute minima I believe the person was referring to the fact that with the best possible combination fo lights etc the lowest
visibility that one could ever make an approach with is 533m.
Every experienced commercial pilot here should be aware that when landing off a CAT1 ILS with an RVR of 550m, the reported visibility will generally be well less than 500m. Therefore a single pilot private operation in current flying practice limiting themselves to an absolute minimum visibility of 535m is clearly putting in a safety factor.
ATC use the absolute minima published for the procedure in terms of RVR. For many CAT 1 ILS this will be 550m. Private pilots using an RVR or CMV of 800m (whatever the visibility) will never have a problem with the CAA even if someone does file an MOR because they are complying 100% with the requirements.