SS
We were discussing two separate issues:
1) Does 91.175 prohibit descent below the MSA other than on a published IAP, in any airspace including uncontrolled
2) Are the IMCR minima mandatory or advisory
I posted the view from an FAA examiner relating to 1) above. I think that he (and this one was a particularly senior one) would know more about it than I would know just reading the FAR/AIM. I agree with you that 91.175 sounds like there is a blanket ban, but I reported an informed view in the USA that in Class G you can do what you like (out there). The other point is that you can fly IFR/IMC down to the MSA (in Class G, without ATC clearance, both in the USA and in the UK) and if you are visual then you can make a visual approach; do you disagree with that?
As for 2) well this one will run and run. I am with Justiciar; having been in business for best part of 30 years I have seen more legalese than I've had Kentucky Fried Chickens and that para was written by an amateur who doesn't even have a decent grip on English grammar. It was not written by a lawyer. That doesn't mean it isn't law, in which case why is it not in the ANO? Everything else IMCR-specific (the 1800m, the no Clall A bit) is in the ANO. Justiciar provides the answer to this.
In general, UK instructors are a very poor place indeed to ask regarding any legal details. I could write for far longer than I have time for, listing the complete and utter bo110cks I have had from them. One instructor told me I could train for the initial IMCR in a particular plane which was on a Private CofA, so long as I owned more than 1/4 of it. Much later I discovered he was involved with the other owners, doing training for them charged as "ground school". Very very hard indeed to know who one can trust in this business. Most instructors live in their own little world, training Joe Public day after day, in between thumbing through airline job adverts. This stuff is way above most of them.
The CAA doesn't make this any easier, with all the advisory stuff they put out which is made to look like it is mandatory. I think a lot of it is written in a kneejerk reaction to some event somewhere...
Finally, to be practical about this, it is unenforceable because nobody can tell when you, the pilot, actually got visual. Unless you have a CAA official sitting in the aircraft. So this isn't a real issue, unless you want to create more traffic on the server. The important thing is to do it safely.