I have 600 “concessionary units” too. They replaced the shares I had held before the company was taken over (by Tui I think) many years ago. They used to give a 50% discount on any of the cross-Channel routes and 40% off North Sea fares. It’s now a more restricted offering, as you say, but still worth having. I find the flexibility of the discounted tickets really useful. I often arrive at the ports early or late, sometimes by a few hours but occasionally by days. If you log on to the the appropriate booking page, using your ID number, you will automatically get the correct ticket and price. I suspect that yours, like mine, are not shares. You and I therefore have no responsibility as joint owners for the appalling behaviour of P&O management.