I have just read an article written by a CAA IR examiner (in the current pplir.org magazine; the current edition is members only) which, if I read it correctly, says that the min vis can be 800m / 1.5 = 533m, with the right kind of runway lights, etc.
The minimum flight manual-authorised usable height for the autopilot also needs to be increased a bit...
According to the article, the approach ban exists only at 1000ft. Before 1000ft, you can continue, and after 1000ft you can continue.
But how all this maps onto different aircraft regs (i.e. is a State of Registry dependent factor) and airspaces (i.e. is an airspace factor like e.g. the UK requirement for an ADF for all IFR in CAS) I have no idea.