Unfortunately, I think NATS are entirely within their rights to pay whatever they like if the fund is in surplus - they are only obliged to pay the underlying rate when its in deficit as determined by the actuaries.
The sticking point for me is that there is no increased protection for post PPP members to a sell-off or contract loss, so new owners can freely move those employees affected to a new scheme. Were this protection in place i think it might make a difference to how some people vote.