Okay, thanks to both of you for the quick replies and the reality check. The ANA flight sounds too close for comfort not to mention cost. Back to Tokyo for our final night it is, then. That is actually okay, much better than rushing/worrying. We have an immediate onward flight Heathrow to Mauritius, so missing the BA departure would be fatal.

Re: "Next time get your outbound flights arranged from KIX or NGO and avoid all the NRT related hassle." Couldn't do it. This is a BA "FIRST" redemption ticket...have to take what we could get.