When I did check in for VS, I can remember being told in training that people travelling together could pool their allowance but weights had to be evened out. So in the VERY common case of wife with heavy bags and husband with lighter bag, we had to ask the wife to take some of her stuff out of her bag and pop it into his. In practice, in the terminal there was no time or space to do this and I let bags go as they were as long as the combined weight was 46kgs, with no bag being over 32kgs.
At the time, I do remember talk of the maximum bag limit at LHR being brought down to 23kgs for health and safety reasons but I don't think it ever eventuated.