You will then take another ten minutes at best to get to BA check-in. It's 75 minutes since you got off NZ2.
Good description of the process,
DCF!. Even as a frequent LHR pax I don't think I'd be able to make it in the time you've described. I think my best NZ2/NZ39-to-tube experience was about 40 minutes and that was with no baggage. Immigration can be incredibly variable at LHR.