BOAC
Certainly in the UK met vis will be issued from MET (and on the METAR) and RVR from ATC so both would be 'in force' and presumably available.
But your decision to go beyond the approach ban is based on what is passed on by ATIS or ATC. It surely takes precedence over potentially expired info published by MET/METAR. And I don't think ATC would ever pass both Vis and RVR.
I can see why the publication of both Vis and RVR on a plate bothers you though. One would think there is a reason...
Talking of approach ban. "Commencement and continuation of approach" was defined in EU-OPS under 1.405. The cross-reference table published by EASA says the equivalent section is now in CAT.OP.MPA.305. There is indeed such a section in Part-CAT, except it only covers visual reference at DH/DA and does not say a word about RVR. Sigh.